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BLUE HILL METEOROLOGICAL OBSERVATORY. 


A. LAWRENCE ROTCH, DrrecrTor. 


EXPLORATION OF THE AIR 


BY MEANS OF KITES. 


I. Kites AND INSTRUMENTS, BY S. P. FERGUSSON. 
II. RESULTS FROM THE KITE METEOROGRAPHS AND SIMULTANEOUS RECORDS AT THE 
GROUND. 


III. DiscussION OF THE OBSERVATIONS, BY H. HELM CLAYTON. 


APPENDIX B. 


EXPLORATION OF THE AIR BY MEANS OF KITES. 
I, — Kites anp INSTRUMENTS. 
By 8S. P. FERGUSSON. 


" Krrus were employed in scientific studies by Alexander Wilson of Scotland, who 
sent up a thermometer on a kite in 1749, and by Benjamin Franklin, about three 
years later, in his well known electrical experiments. 

Systematic explorations of the air by kites carrying instruments have been at- 
tempted only in recent years. One of the earliest of these investigations was under- 
taken in England by Mr. Douglas Archibald in 1883, the object being to ascertain 
the rate of increase of wind velocity with increase of altitude. The instruments 
carried by the kites were small Biram anemometers, indicating by means of dials 
the total movement of the air from the time the instruments left the ground until 
their return.” 

At Blue Hill Observatory kites were used in making observations of atmospheric 
electricity by Mr. Alexander McAdie during the summer of 1885, and again in June 
and July, 1891, and July and August, 1892" \ (Harvard Annals, Vol. XL. Parts I. and IT.) 
The kites employed were tailed kites of the ordinary hexagon pattern, and were 
coated with tin-foil, which served as a collector of the electricity that passed down 
a copper wire to the electrometer at the ground. No high flights were attempted. 

In July and August, 1894, Mr. William A. Eddy of New York, who had been 
very successful in reaching great altitudes with kites designed by himself, spent 
two weeks at the Observatory for the purpose of elevating instruments with’ his 
kites. After a few days of experiment, it was proved that the Eddy kites could 
raise self-recording instruments; and on August 3, an ordinary Richard thermo- 
graph was altered for use in the experiments. The parts usually made of iron and 
brass were replaced by others made of hard rubber and aluminium, and the modified 
instrument, including a basket inverted over it to screen the bulb, weighed 1.1 kilo- 
grams. On August 4, 1894, this instrument was raised 436 meters (the height being 


44633 


49 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


determined from angles observed at two stations 100 meters apart), and an excellent 
record of temperature was obtained. Five Eddy kites, having a total area of nine 
square meters, were employed. This experiment was repeated successfully on August 
15, and a detailed account of both flights, prepared by Mr. Clayton, was published in 
the American Meteorological Journal for December, 1894; details of the kites and 
instrument were also published in the Scientific American for September 15, 1894. 
It is believed that these are the first instances of the elevation of self-recording instru- 
ments by kites. Self-recording instruments are those which record their indications 
graphically and continuously on paper, with ink or otherwise, in such a manner that 
the records may be preserved. This definition is given in order to distinguish such 
instruments from simple indicating or registering instruments provided with dials 
or scales only, and from which the indications are obtained by means of direct eye 
readings. The great superiority of a continuous record to eye observations even at 
frequent intervals has long been recognized, but until recently self-recording instru- 
ments have not been made sufficiently light to be suitable for use with kites. Prior 
to 1894, thermometers had been raised to heights of about 500 meters, and kites 
alone had been flown as high as 1,700 meters, indicating that light instruments 
could be easily carried to great heights by means of ordinary kites. Hence the 
chief difficulty encountered was that of obtaining recording instruments adapted to 
use with kites. The tables of observations following this paper show that the average 
altitude of the first 22 flights at Blue Hill is almost as great as the average height 
reached in the 22 ascents of the Berlin captive balloon in 1890-92. (Meteorologische 
Zeitschrift, September, 1895, page 344.) 

The following is a brief historical sketch of the work at Blue Hill. The first 
selfrecording instrument (a thermograph), was raised on August 4, 1894; the first 
baro-thermograph, on August 19, 1895; the first Hargrave kite constructed at the 
Observatory was flown on August 18, and the baro-thermograph was elevated with 
this form of kite for the first time on September 21. The first thermo-anemograph 
was constructed in November, and this instrument (probably the first of the kind to 
be elevated by kites) was used regularly on and after November 16. Music wire 
was employed for kite line instead of cord on and after January 27, 1896. During 
this month, water-proof kites were employed during rain and snow storms. The 
height of one kilometer above the hill was reached for the first time on April 13. 
A baro-thermo-hygrograph of aluminium, constructed by Richard of Paris, was used 
for the first time on April 8, although similar heavier instruments had been carried 
in balloons. A height of 1.8 kilometers, or over one mile, was reached for the first 
time on July 20. At the suggestion of Mr. Douglas Archibald, a tail composed of 


i 


EXPLORATION OF THE AIR BY MEANS OF KITES. 43 


hollow cones was attached to one of the kites for the first time on July 23. A height 
of 2,000 meters was reached on August 1. The maximum height above Blue Hill, 
2,665 meters, reached on October 8, is probably the greatest which a kite had 
attained at that time. 

‘The primary object of the experiments was to obtain meteorological records at 
the highest possible elevations; and in attaining this result the forms of kites and 
accessory apparatus already known were employed at first, and such changes were 
made from time to time as seemed advisable from considerations of economy and 
increased efficiency. ) Much credit is due to Mr. William A. Eddy for his efforts to 
improve the kite, and to make it a useful instrument; and his personal assistance at 
the beginning of the experiments was of great value. Acknowledgments are also 
due to members of the Boston Aeronautical Society, to members of the Boston 
Scientific Society, and to Captain C. D. Sigsbee, U. S. N., for encouragement and 
assistance ; also to Professor C. F. Marvin, who is in charge of the kite experiments 
of the Weather Bureau in Washington, D. C., and who has kindly allowed the 
Observatory staff to examine his apparatus. 

The collection of meteorological data has occupied most of the time devoted to the 
experiments; therefore the improvements in the kites have not, perhaps, been so 
great in some respects as they might have been had the kite, as an instrument, been 
carefully and thoroughly studied before beginning the flights with the meteorograph. 
Some very useful and important advances have been made, however, and the plan 
followed has proved advantageous in indicating by practical experiment the kites 
best adapted to the work, and also in obtaining valuable meteorological records ; 
thus securing the most economical use of kites and accessories. The experiments 
were conducted under the direction of Mr. Rotch; Mr. Clayton has had charge of 
the experiments with the Hargrave kites, and the reduction and discussion of the 
records; Mr. Sweetland has assisted in the flights, and in the reduction of the 
records; while the writer has had charge of the experiments with the Eddy kites, 


and has devised the mechanical appliances and instruments. 


Metuops or ConstrucTING AND FryinG KITEs. 


Conditions under which Experiments were made. —Since the pressure of the wind 
alone is utilized in experiments with kites, the first step was to consider the means 
for employing this power to the best advantage. In order to obtain a clear under- 
standing of the conditions to be met, it is well to give briefly the results of observa- 
tions of wind velocity on Blue Hill. At this Observatory, the average recorded for 


the summer months is 7.5, for the winter months 9.3, and for the year 8.4 meters per 


44 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


second. Near the ground the wind is extremely variable, the oscillations on either 
side of the mean velocity usually amounting to fifty per cent of the mean, and often 
exceeding this limit. The wind becomes steadier with increasing altitude, and the 
pressure becomes proportionally less on account of the decrease in density of the 
air with increase of altitude. But, since the pressure upon flat surfaces exposed 
normally to the wind increases in proportion to the square of the velocity, this rel- 
ative decrease of pressure, due to rarefaction of the air, is not so rapid as the 
actual increase due to increase of velocity. From observations of clouds it has been 
ascertained that the velocity increases from 7 meters per second near the ground 
to 28 and 44 meters per second, respectively, for the summer and the winter half- 
year at an elevation of 9,000 meters; while, even at altitudes already reached by 
kites, it averages between 10 and 25 meters per second. Marked variations from 
these average conditions frequently occur, and it is safe to say ‘that, for continuous use 
under average conditions at high altitudes, the kite must be light enough to be lifted 
by a wind of 5 or 6 meters per second, and strong enough to fly safely in winds of 15 
to 25 meters per second; or, otherwise stated, strong enough to resist a pressure ten 
to fifteen times greater than that required to lift the kite. Obviously, the materials 
and workmanship must be of good quality to insure uniform results under such trying 
conditions, and in the experiments at Blue Hill they received first consideration. 

Materials used in Framing Kvics.— Of all materials used in constructing the frames 
of kites, spruce wood of fine quality proved the best, and, except for experimental 
purposes, it has been used in the construction of all the kites. Spruce wood is one 
of the lightest for its strength obtainable, and it is also quite elastic. Comparisons of 
the strength, etc. of different woods may be found in Lanza’s Applied Mechanics 
and ‘Thurston’s Materials of Engineering. Some tests of white pine, and of poplar 
wood, and of steel umbrella-ribs were made at Blue Hill to ascertain their fitness for 
use in kite frames, but none of these materials equals spruce wood. The umbrella- 
ribs are heavier than spruce or white pine, and, without a complicated system of 
braces to stiffen them, are entirely too flexible. The expense and difficulty of work- 
ing tubing made of steel and aluminium prevented experiments with these mate- 
rials, although it is probable that light tubing might be used to advantage. In 
selecting spruce, it is necessary to obtain sticks entirely free from knots, and having 
a straight grain. <A stick with the grain running diagonally is more easily broken 
than one containing a knot; but each is weaker than a straight-grained stick free 
from knots. The wood next best to spruce is white pine, which is more easily 
obtained than spruce. Bamboo rods were used in one kite, but it was almost impos- 
sible to secure a piece of uniform strength and rigidity. 


EXPLORATION OF THE AIR BY MEANS OF KITES. 45 


Materials for Covering Kites. — For covering kites, several varieties of paper and 
cloth have been tried, and of these bond tracing-paper, nainsook, and silk are con- 
sidered best. Common newspaper is too weak to be of use. Manila drawing-paper 
is excellent, though heavy; it may be obtained of various weights in wide sheets or 
rolls, —a great advantage in the construction of large kites. Bond tracing-paper is 
the strongest for its weight of all paper tried, and while its cost was about twice that 
of manila paper, it is only half as heavy, and is much tougher and more durable, — 
advantages that more than offset the greater cost. It may be had in rolls of fifty 
yards, the usual width being one yard (0.9 meter). Nearly all the kites used in the 
first year’s experiments were covered with bond-paper, and under favorable conditions 
it gave excellent results. a 

The advantages of paper coverings are: (1) imperviousness to air; (2) smooth- 
ness; and (3) ease of preparation. Kites covered with paper, especially those of 
the Eddy pattern, appear to fly higher than those covered with cloth. The disad- 


vantage of paper is its great lack of durability, —a very great disadvantage. When 
in use small punctures are made in the covering almost every time the kite touches 
the ground, and in time these so weaken it that it will not withstand an ordinary 
increase of wind pressure. Coverings of paper, especially those of large kites, will 
not endure long in a wind exceeding 12 meters per second; and in sudden gusts 
they have sometimes been blown into shreds before the wind became strong enough 
to affect the stability of the kite. 

For cloth coverings, calico, common sheeting, cambric, percaline, nainsook, 
and silk have been tried. Calico is the cheapest of all these, and is light, but 
not strong or durable, and the widths are usually too narrow. Ordinary sheeting 
was the strongest material tested, but also the heaviest, and there is little to be 
gained by using it. Its chief advantage is the width: it can be obtained in 
pieces three yards wide. This simplifies the construction of large kites. Lonsdale 
cambric and percaline proved decidedly better than sheeting, because they are 
smoother, more closely woven, and much lighter than sheeting. The cost per 
yard is about the same as that of sheeting, but the width is usually one yard or 
less. Nainsook was found to be the best of the cotton cloths, although the most 
expensive. It is lighter than all others that were tested, and stronger than all 
others except sheeting. It can be had in widths of one meter or less. Silk is, 
no doubt, the lightest of all fabrics in proportion to its strength, but the samples 
tried were not very durable. Its other disadvantages are its narrowness, for it 
seldom exceeds thirty inches in width, and its cost, which is more than twice that 
of cotton. The lack of durability and the great cost make it doubtful if there 


46 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


is much to be gained by using silk; nainsook is slightly heavier, but has the advan- 
tages of greater durability and smaller cost, which more than compensate for the 
greater weight. 

The advantages of cloth covers are: (1) durability ; (2) strength; and (3) the fact 
that they are not appreciably affected by moisture when used in rainy weather. 
Cloth covered kites apparently do not fly as high as paper covered kites, but this 
defect has been removed by filling the meshes of the cloth with several thin coats 
of varnish. Unfortunately, cloth so treated becomes brittle or rotten soon after- 
ward, and in a few weeks is no better than paper. At the recommendation of 
Dr. J. E. Stanton of Boston, a’ varnish made by dissolving rubber in carbon disul- 
phide was tried with good results, and one kite that has proved very durable was 
covered with the following mixture : — 

Pures UpUR tase 5) ate meee 


Sparvarnish.. «. . . 4/07, 
Carbon disulphide . . 2 Ib. 


The rubber should be cut into very small pieces and dissolved in the carbon 
disulphide. This process requires several days. The varnish is then added, and 
the mixture is thinned with turpentine. Four very thin coats were applied to the 
kite, the first coat being allowed to dry before applying the others, Further experi- 
ments are necessary in order to determine the best varnish, because very few 
varnishes have been tried at Blue Hill. 

Materials for Flying Kites. — Both cord and wire have been used successfully in 
constructing and in flying kites, and various specimens of different weights and 
strengths have been tested in order to select those of the greatest strength and 
durability. To obtain the average strength of any cord, a length of not less 
than 7 meters (23 feet) was tested by securing one end of the sample to some 
rigid support and the other to a strong spring balance, and then by pulling 
upon the balance until the cord broke. To measure great strains easily, one 
end of a rope was secured to the ring in the frame of the spring balance, while 
the other end was wound around the drum of the windlass. Specimens of most 
cords were broken several times in succession, in order to determine the average, 
as well as the extreme breaking strains. The results of the tests are shown in 
Tables XIII. and XIV. 

The values given are approximately correct, but the cords vary considerably 
in weight, size, and strength. Weak places, less than half as strong as the aver- 
age of certain samples, were found in some of those tested, and, to provide against 
loss, it was found necessary to test every piece of line used. One important 


EXPLORATION OF THE AIR BY MEANS OF KITES. 47 


TABLE XIII. 


Diameter Weight per Average 


100 Meters: Breaking 


in Sreakir 
Millimeters. Kilograms. Strain in 
Kilograms. 


Kind of Cord. 


Flax sole-thread, No. 8 0.10 36.3 
“: “ ake St, 0.17 37.5 
Braided fishing line: 
Large, flax, soft-braided 0.75 63.5 
Small, silk, ge “op 5 
ve “  hard-braided J ae sts 
Mattress twine, No. 13 ; ; 0.28 ped | 
Cable-laid cord, “ 18 E 0.29 DAY 
0.30 27.2 
0.42 35.4 
0.46 40.8 
0.56 55.0 
0.66 61.2 
0.73 81.6 
0.84 108.9 
1.18 136.1 


ae 


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wo oo p> bp 


Or dD Oo & 


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result of the tests was that some cords, proving very strong during the first test, 
rapidly became weaker when subjected repeatedly to a breaking strain, Certain 
cords selected for great strength, while in actual use as line for the kites, broke 
under strains much less than that adopted as a safe working strain; and, to ascer- 
tain if these cords actually became weaker, a few new samples were broken several 
times in succession. The results of some of these tests are as follows: — 


TABLE XIV. 


Breaking Strain in Kilograms, I r 
Kind of Cord. 4oss in 


Number 
Kilograms. Pere 
First Test. Last Test. . 


Sole-thread, No. 8 40.8 34. 6.7 

ee Coie 45.4 
Fishing line (large) 70.0 
Blocking cord, No. 20 83.8 


These tests show that the blocking cord was the most durable, the loss being 
but 3 kilograms out of over 80. The cords least durable were the shoe-threads and 
braided fishing lines. The shoe-threads are loosely twisted fibres of flax, and are 


* Estimated. 


48 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


very flexible. As the table shows, these cords were the lightest of all, considering 
their strength, but were not sufficiently durable for use as lines for flying kites. 
The braided fishing lines were samples sent to Blue Hill by a manufacturer, to be 
tested. They consisted of a few straight fibres of silk, or of linen, over which was 
braided a cover of the same material. Hard and soft braids were tested, but there 
appeared to be very little difference in strength between the two kinds. The sam- 
ples were quite strong, but the durability of these was little greater than that of 
the sole-thread. The mattress twine was a twisted flax line and was strong con- 
sidering its weight, but no large sizes were procurable. It was not so durable as 
the blocking cords. The cable-laid twines and the blocking cords (which resemble 
cable-laid twine) were the best and most durable of all the cords tested. These 
are hard-twisted linen lines and are obtained of several sizes and strengths. They 
are heavier than the shoe-threads and the braided lines, but their great durability 
renders them superior to loose-twisted and braided lines. Blocking cord was used 
for a main line during 1894 and 1895, a line 1,160 meters in length being employed 
until January, 1896; and it has since been used as secondary lines for kites flown 
tandem. The length of single pieces of cord was usually less than 100 meters, and 
in uniting several short lengths to form the main line great care was taken to 
secure strong knots and splices. The knot used by Mr. Eddy is called by him the 
surgeon’s or the fisherman’s knot, and, being easy to tie and very durable, it was 
used in making up the main line. This knot is shown in Plate II. Figure 12. The 
bowline knot was also used in some parts of the line. This can be recommended as 
a good knot, although it is less compact than the surgeon’s knot. For attaching lines 
to the kites, an ordinary running noose is generally used, the knot being tied with a 
loop so that it can be readily loosened. For attaching secondary lines to the main 
line, the device shown in Plate II. Figures 9 and 10 was used at the suggestion of 
Mr. J. B. Millet. Two half-hitches are formed in the main line, and these are tight- 
ened around an eyelet into which the secondary line is tied or secured by means 
of a toggle, as in Plate II. Figure 4. The eyelet is easily removed when the strain 
is taken off, and is a perfectly safe device for attaching secondary lines, or instru- 
ments, to the main line. 

Cord proved to be excellent for ascensions to small heights, but, on account of 
its great weight and large surface exposed to the wind, it was almost impossible 
to reach altitudes of 600 meters while using it as a main line. The area of the line 
of 1,100 meters was nearly 3 square meters, and, although this surface was never 
normal to the wind, the effect of the pressure of the wind was so great that the 


angular elevations were generally low. 


EXPLORATION OF THE AIR BY MEANS OF KITES. 49 


Steel music wire, commonly known as “ piano wire,” having been used in deep- 
sea sounding, and by Archibald in his experiments with kites, this material was tried 
for a main line. Upon request, early in December, 1895, Captain C. D. Sigsbee, 
U.S. Hydrographer, kindly furnished the Observatory with information concerning 
the use and care of wire, but it was not until January 27, 1896, that the sample 
of wire first obtained was used as a main line. This sample proved very satisfactory 


g, and more wire was purchased from time to time, until, by 


from the beginning, 


September 15, the main line employed was 5,500 meters in length. Two sizes of 
wire have been used, and the chief elements of these are given below: — 


Music Wire Gauge : Diameter: Weight per 100 Meters: Breaking Strain : ° 
Number. Millimeters. Kilograms. Kilograms. 
12 0.71 0.34 90 to 96 
14 0.81 0.42 131 “ 140 


Referring to Table XIII., and comparing the above measurements of wire with those 
of the strongest cords, it will be seen that the wire is less than half as heavy and 
less than one fourth the size of cord of the same strength. Figures 7 and 8 (Plate IL.) 
show approximately the size of music wire and blocking cord of the same strength. 
Also, the wire is polished smooth, which reduces the friction caused by wind blowing 
past it. Music wire, being highly tempered, is easily injured by the formation of 
small sharp bends or kinks, and care must be taken to keep it taut when unwound 
from the reel or the coil. Single pieces 2,500 meters in length may be obtained 
from the manufacturers; hence but few splices are necessary in a line of considerable 
length. The methods of splicing this wire are different from those used in uniting 
telegraph wires, since for the sake of durability and safety, no close twists or bends 
should be allowed in music wire. The splice used at Blue Hill is similar to one 
recommended by Commander Sigsbee, and is made as follows. The ends of the wires 
to be united are thoroughly cleaned and laid together, not twisted, for a number 
of turns, as shown in Plate II. Figure 6; then a seizing of very small annealed 
wire is put on near each end. The extreme ends of the wire are wrapped close 
around the standing parts at the end of the splice, and the whole is covered with 
soft solder by means of a soldering iron or, still better, by drawing the splice 
through a groove in a piece of board in which a small quantity of solder is kept 
fluid by means of a soldering iron. By the use of this method all danger of weaken- 
ing the wire by overheating it is avoided. The length of the original Sigsbee splice 
was about 18 centimeters, but it was found necessary to increase the length to 30 
or 35 centimeters in order to insure durability. To acquire the knack of laying the 


wires together uniformly takes some practice in order to make a strong, durable 


50 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


splice; but the knack is easily acquired, and the only tools necessary are a soldering 
iron and plyers to hold one end of the splice while the wires are being laid against 
one another. Projecting ends of the wires may be removed by means of cutting 
plyers. The splice may be smoothed by a file or by sand-paper, but this is not 
absolutely necessary ; and since all abrasions of the single strands of wire reduce 
their strength, filing should be done carefully, and only upon the parts of the splice 
covered by solder. The method of attaching kite lines, etc. to the end of the 
wire is shown in Plate II. Figures 4 and 5. The end of the wire is coiled twice 
around an eyelet, and the free end is spliced with the standing part in the same 
manner as that shown in Plate II. Figure 6. Since this connection receives more 
usage than other splices, it is important to exercise, if possible, greater care in 
preparing it. The loops around the eyelet must be so tight that the eyelet cannot 
be forced from them by unequal strains, and the end of the splice must be made 
smooth to avoid loosening the wrapping, should the wire be dragged over any 
obstacle. 

For attaching secondary lines at any point on the main wire, the clamp shown in 
Plate IT. Figure 11 has proved very satisfactory. The clamp consists of an angular 
casting of hard aluminium, the ends of which are slotted to receive the wire. The 
slot is cut by a saw slightly thinner than the diameter of the wire, and is opened by 
a wedge until the wire will pass just behind the clamp screws. Ordinary thumb- 
screws for use by hand, or machine screws for use with a screw-driver, may be used 
to tighten the clamp. ‘The clamp is secured to the wire with the short arm toward 
the outer end of the wire, so that the pull of the secondary line will be nearly. 
equal upon both arms. The secondary line is attached by the running noose, bow- 
line knot, or, still better, by the toggle shown in Plate II. Figure 4. No injury to 
the wire has occurred since this clamp was used, and its only defect is that 
considerable time is required for its attachment and detachment. Attempts have 
been made to devise a clamp that could be attached and detached instantly, but 
so far without success. Eyelets can be secured to the wire in the same manner 
as to cord, but, on account of the difficulty of handling the wire while it is under 
strain, they were not often employed. Eyelets fastened permanently to the wire 
are objectionable, because when they are used kites can be attached only at 
fixed points, and moreover the winding of the wire over eyelets or other obstruc- 
tions produces noticeable bends that may in time weaken the line. Slight bends 
are apt to crack or to split when they are straightened and bent many times, 
as occurs when the wire is used repeatedly; they are always a source of danger. 
It is the practice at Blue Hill to keep the line entirely free from sucli defects. 


EXPLORATION OF THE AIR BY MEANS OF KITES. 5] 


Windlass. — During the first season’s experiments, the windlass consisted of a 
large spool, such as is used in storing insulated wire, mounted in a suitable box, 
which was secured to a wheelbarrow, for convenience in moving it about. A 
device for measuring the length of the line was attached in August, 1895. This 
rather crude windlass served its purpose very well, but was not very strong; and 
in September, 1895, it was replaced by the heavier apparatus, shown in Plate II. 
Figures 15, 14, and 15. This was built after the pattern of the ordinary portable 
hoisting windlass. The frame is of hard wood, and is mounted upon wheels. 
The drum, A, containing the cord or wire, is 15 centimeters in diameter and 30 
centimeters in length, and is provided with heads 35 centimeters in diameter, 
which are strengthened on the outside by iron flanges 15 centimeters in diameter 
and 2 centimeters thick. The drum is clamped to a steel shaft 2.5 centimeters 
in diameter, and provided at each end with a crank, G, G. To regulate the speed 
of the drum when line is reeled out, a hand-brake, /, is arranged to bear against 
one of the drum-heads. The device for measuring the line is secured to the frame 
in front of the drum. It consists of a hard-wood grooved pulley, B, exactly 50 
centimeters in circumference, and is provided with registering dials (shown at C) 
for indicating the number of revolutions. The pulley and dials are mounted in a 
frame which also carries an oil reservoir, D. This register moves freely backward 
and forward upon the guides H and J, and thus adapts itself automatically to all 
changes in position of the wire. The stops, J, Z, serve to limit the movements of 
the register, and they can be clamped in any desired position. The position taken 
by the wire is shown by the line Z. It passes under the pulley without going 
entirely around it. This register was carefully tested by winding known lengths of 
line through it; and the tests show that it is extremely accurate, the errors rarely 
amounting to one half of one per cent. The uniformity of its action is shown by 
the fact that the dials have not registered an excess or deficiency amounting to 
20 meters since the beginning of the experiments. The largest differences were 
observed when over 5,000 meters of line had been let out and reeled in, making 
10,000 meters in all, with a difference of but one fifth of one per cent. There is 
very little, if any, slipping of the line when it passes under the pulley at speeds 
varying from 1 meter to 5 meters per second. The length of line let out is read 
directly from the dials, without the necessity of applying a correction for the varying 
amount of wire on the drum, as is necessary when a register is connected with 
the axis of the drum. 

To prevent the wire from rusting it is necessary to keep it covered with oil. 
A satisfactory method of applying the oil is to allow a small quantity to drop from 


Or 
bo 


BLUE HILL METEOROLOGICAL OBSERVATIONS. 


the reservoir, Y, upon the measuring pulley as the wire passes under it. The flow 
of oil is regulated by a stopcock; and usually about 25 drops per minute prove 
sufficient. In extremely cold weather, when oil solidifies, the wire is passed over 
cloths saturated with oil or grease. 

The simple drum of hard. wood, already described, proved strong enough for 
storing cord under considerable strains; but after wire was adopted for a main line, 
the drum-heads were spread apart when a thickness of scarcely 2 centimeters of 
wire had been wound on the drum at a moderate strain. The drum next made 
was of hard wood, the core being 18 centimeters in diameter and 15 centimeters in 
length; it was provided with heads 27 centimeters in diameter and 3 centimeters 
thick. Outside the heads are placed flanges of the same diameter as the heads, and 
2 centimeters thick. The heads are prevented from spreading by three iron bolts 
passing lengthwise through the core of the drum. This drum was in use during 1896 
until October, when it was replaced by the one illustrated in Plate Il. Figure 15. 
This is essentially the same as the preceding, except that it is twice as long, and the 
heads contain a recess into which the core fitted. This recess was made to provide 
for spreading apart of the drum-heads in case the crushing effect of the wire became 
excessive. In the figure, A is the core, of hard maple, the ends of which fit smoothly. 
to a depth of 1 centimeter, into the heads A, A, which are 4 and 6 centimeters 
thick respectively. The flanges, Z, LZ, and the heads, are securely held to the core 
by the bolts, JZ, JZ, which are placed beneath the surface of the core. The drum 
complete, with two cranks 20 centimeters long, weighs 40 kilograms. One of the 
heads is very thick, to provide a good bearing surface for the brake. This drum 
proved strong enough for the work, but the crushing effect of the wire will probably 
destroy the wood which is immediately exposed to it; and it seems that the only 
drum suitable for continuous use should be made of heavy cast iron or of steel. The 
pressure of the wire appears to be proportional to the number of turns wound upon 
the drum, and, according to a calculation by Commander Sigsbee, this pressure some- 
times amounts to several tons for each layer of wire. The drum used by Sigsbee was 
about 0.5 meter in diameter, and was built of steel. On a drum of this large size, the 
pressure of the wire is not so concentrated as it is upon one of smaller diameter. 

One method of avoiding the excessive and cumulative strain of the wire, em- 
ployed in deep sea sounding apparatus, is to use the strain-pulley. Several turns of 
the wire are passed around a grooved pulley, the wire on one side leading on, and 
on the other passing off to a storage drum turned by a loose belt which moves it 
with force only sufficient to receive the wire under a ‘very slight tension. Such 
a device would make the portable windlass much more complicated, and perhaps too 


EXPLORATION OF THE AIR BY MEANS OF KITES. 53 


heavy to be easily moved; therefore it was not adopted. Full descriptions of this, 
and of other devices for handling wire, are given in Commander Sigsbee’s book, 
Deép Sea Sounding and Dredging (U. S. Coast and Geodetic Survey, 1880). One 
of these devices is that used for transferring a loose coil of wire to the drum of 
the windlass. Music wire is usually sold in coils, and to wind it upon the drum 
of the windlass it is necessary to mount each coil upon a spool so that the winding 
may be smooth and kinks may be prevented. This special device has not been used 
at Blue Hill, because, upon request, the manufacturers wound the wire upon spools, 
and its transfer to the windlass was easily and safely effected. 

Cranks of 20 and 30 centimeters in length were tried, and the labor of winding 
was less when the shorter cranks were used; therefore these cranks were adopted for 
general use. The complete windlass, with 5,500 meters of wire on the drum, weighed 
about 150 kilograms, but it could be moved easily by one man, and placed in any 
favorable situation. In this respect, it was superior to a stationary windlass, because 
there is no place on the summit of the hill where the exposure is uniformly good, 
except on the Observatory tower, and there the line would interfere with the 
instruments. 

Dynamometer.— The pull upon the line was measured by attaching an ordinary 
spring balance to the drum. Frequent readings of the balance gave valuable data 
concerning variations in the pull. It was decided to make this device self-recording, 
but though the mechanism has been designed, as yet it has not been constructed. 

In addition to the knowledge concerning the pull of the kites gained by using 
the dynamograph, an approximate measure of the wind velocity may be obtained 
if but one kite is attached to the wire, provided due allowance is made for the 
weight of the wire and the kite, the density of the air, and the angle of inci- 
dence of the kite to the wind. However, such results at best are inferior to direct 
measurements of wind velocity, and they require much more work; and as at 
least two kites were always attached to the line, the method is not used at 
Blue Hill. 

Instruments for Measuring Angles. — During the first experiments, the angular 
altitudes of the kites were obtained by means of the rough altitude instrument 
shown in Plate II. Figure 16. Upon a board, A, one edge of which is provided with 
sights at the corners, C and D, is graduated an are of a circle, the centre of which 
is the corner C. From this corner is suspended by a light thread the weight B. 
When the edge C D of the board is in a horizontal position, the cord intersects the 
graduated are at its zero, 0. On raising the end of the board, as shown in the figure, 
the cord passes over successive divisions of the arc, and indicates the inclination of 


54 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


the edge C D with the horizon. To make an observation, the sights C, D, are set to 
coincide with the line of sight from the eye to the kite, or to the meteorograph, 
and the string indicates the altitude. During 1895 was used a Casella pocket, alt- 
azimuth, which differs in principle from the instrument just described in that the 
altitude is measured by a pivoted graduated disk which is loaded on one side. The 
disk always hangs with the loaded side down, and when the sighting tube, to which 
is secured the index, is inclined from the horizontal, the index shows the amount of 
inclination. This instrument is more accurate than the one first described, and the 
readings are probably correct within one degree of arc. In the spring of 1896, a 
rough transit was made, the circles of which are 13 centimeters in diameter, and are 
graduated to half-degrees. The telescope magnifies about ten diameters, and the 
readings are usually correct within 0°.3, which is sufficient for the purpose. 


KITES. 


The following kites have been tried at Blue Hill : — 

Archibald’s flat diamond-shaped kite, with tail composed of hollow cones. 
Cabot’s rudder kite. 

Eddy’s tailless kite. 

Eddy’s kite, with cross-stick in the form of a dihedral angle. 

Clayton’s keel kite. 


Hargrave’s cellular kite. 


Ioan FR wh HY 


Clayton’s modified Hargrave kite. 

A number of modifications of the above kites also were tried. 

1. The coverings of the tailed kites were from the original kites employed by 
Mr. Archibald in his experiments in 1883. They were purchased of Mr. Archibald 
by Mr. J. B. Millet, who kindly sent them to the Observatory for trial. The original 
frames were of a fine quality of bamboo, but, this material being difficult to obtain 
in Boston, the new frames were of spruce. Two sticks were used, the central stick 
being 1.5 and the cross-stick 1.0 meters in length. The sticks were lashed together 
at a point about one third of the length of the central stick from its upper end, and 
their ends were fitted into pockets at the corners of the covering, which was made of 
Tussore silk. The tail consisted of a cord five or six times longer than the kite, 
carrying at its lower end two or more light cones made of cloth. The cones are 
attached as shown in Plate III. Figure 21, with the open ends toward the wind. 
A ring in the open end prevents collapsing of the cone. This kite, although seem- 
ingly very stable through a wide range of wind velocity, did not attain a high 


angular altitude, and it was never used in the flights with instruments. 


EXPLORATION OF THE AIR BY MEANS OF KITES. 55 


2. This kite was designed by Mr. Samuel. Cabot of Boston, -who has constructed 
some very large kites of this pattern. The kite is of the well known hexagonal 
shape, and at the rear end is secured a disk-like rudder (see Plate II. Figure 22). 
A is the kite, which is here represented as a single flat surface, and £& is the rudder, 
formed of a hoop of very flexible bamboo covered with cloth and firmly lashed to the 
frame of the kite. The specimen tested at Blue Hill was about one meter long and 
a half-meter wide. It flew quite steady in winds averaging 3 to 8 meters per second, 
and reached a high angular altitude, but it was unstable in winds stronger than 
8 meters per second. One remarkable feature of this kite was its stability after 
the string was released. On one occasion, when the kite was attached to about 60 
meters of light cord, it broke away, and before falling to the ground it was carried 
1.6 kilometers, a horizontal distance of twenty times its vertical height above 
the earth. 

3. The details of Eddy’s kite are shown in Plate III. Figures 17 to 20. This kite 
consists essentially of two sticks, AB and CD, of nearly equal length, crossed at 
right angles. They are lashed together at a point distant from the top by 18 per 
cent of the length of the central stick, C.D; the cross-stick, A B, is bent backward 
in a bow (the depth of which is about 10 per cent of the length of the stick) by 
means of a cord attached in the usual manner of a bow-string. The ends of the 
sticks are notched to receive the cord which forms the edge of the kite. This cord 
is firmly secured to all the corners except the one at the top, where it is usually tied 
with an adjustable bow-knot. It is important that the sides of the kite, AD and 
BD, should be equal, so that the surface of the covering may be equally divided 
between the two sides of the central stick, CD. This kite is easily constructed and 
is a distinct advance beyond other single surface kites. The angular height attained 
was greater than that of the other kites; and the best made Eddy kites flew with 
steadiness through a wide range of wind velocity. It seemed desirable to improve 
this kite still more; and while the same proportions are retained in the later forms 
of this kite, the construction is now very different. 

4. The weakest part of the original kite was the bowed cross-stick, AB (Plate HI. 
Figure 17). While bent, this stick is constantly under strain, which increases when 
the kite is flown, because the pressure of the wind forces the stick backward in the 
direction in which it is bent. In some of these kites, especially those of larger sizes, 
the cross-stick is bent backward by the pressure of the wind alone. This strain is 
liable, if the stick is not of uniform strength, to bend it unevenly, causing the kite 
to sag badly toward the bent side; or if the stick is of uniform strength, it is easily 
broken in strong winds. The form of cross-stick shown in Plate III. Figures 19 


56 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


and 20 was adopted as a substitute for the bow. It has proved very satisfactory, 
not one in ten having broken. This device is nearly the same as that used by Sir 
George Nares in 1861, in the storm-kite designed by him, and which is described 
in the Scientific American Supplement for September 10, 1892. In the figures, 
B is a short piece of square tubing, one side of which is slotted to receive the 
central stick, A. The ends of the two pieces forming the cross-stick, D, D, are 
driven into the open ends of the tubing, which is bent at the slot to the desired 
angle, as in Plate III. Figure 19. When this is done, the jaws of the slot clamp the 
central stick firmly, and usually no lashing with cord is necessary. A piece of wood, 
, is secured firmly to the cross-sticks, which may be further strengthened by the 
brace, /. An advantage of this form of construction is, that, if one stick becomes 
damaged, it may be replaced by a new one without disturbing the others. All 
the joints are first coated with glue, and then with varnish or with paint. Greater 
rigidity of the frame is obtained by sticks made in the form of a T-rail, as in 
Plate IJ. Figure 20. Two flat sticks, say of 1 x 2 centimeters in cross-section, are 
secured together by glue and brads, with the edge of one against the flat side 
of the other. Varnish or paint will prevent this joint from working loose in 
damp weather. 

Following a plan suggested by Dr. Stanton, the cover of the kite was made 
separate from the frame, and then tied to it. In order to do this in the best manner 
a diagram of the actual size of the kite (see Plate III. Figure 17) was drawn upon the 
floor of the workshop, and screws were placed at the corners A, B, C, and D, with 
their heads projecting about one centimeter above the surface of the floor. The cloth 
cover was then tacked to the floor outside the edges of the diagram, and the screws 
were forced up through it. The cord for the edges of the kite was then placed outside 
the screws, and was tied at the upper corner, C, a knot also being made just below 
each of the corner screws at A and B, in order to prevent the ends of the cross- 
stick from slipping when the cover is tied to the frame. The cover was pasted over 
the cord, the paste being rubbed in thoroughly, and a uniform smooth seam was made 
except at the corners, where the cord was left bare for about five centimeters. The 
completed cover was not removed from the screws until it was thoroughly dry. The 
bare portions of the cord at the corners were firmly lashed to the ends of the sticks, 
care being taken to bring the knots at 4A and B firmly against the lower edges of the 
cross-stick. The ends of the cross-stick are liable to slip downward when the cover 
is tightened, and the knots check this tendency very satisfactorily. The cover was 
firmly lashed to the sticks at the corners except at the top, C. At this point, the 
ends of the cord, which are left bare for a distance of several centimeters, are united 


EXPLORATION OF THE AIR BY MEANS OF KITES. 57 


by means of a square bow-knot, and are placed in the groove in the top of the stick. 
This provides’ for adjustment of the tension of the cover, which, as the kite is used, 
requires occasional tightening. 

The bridle or hanger is attached as shown in Figure 18. The upper part of the 
bridle, G, forms nearly a right angle with the surface of the kite at #, and in length 
from / to J is usually equal to one half of the width of the kite from A to B. The 
ring J, to which was attached the flying string, is secured to the bridle by a half- 
hitch, its exact position being determined by experiment for each kite; but it is 
usually placed between the two cross-marks shown in the figure. 


TABLE XV. 


ELEMENTS OF THE EDDY KITES. 


Length of 
Approximate Total ae 
Designation Size of Sticks: Area of Weight | Weight per 

of Kite. Central Cross- Millimeters. Cover : of Kite; | Sa. Meter: 
Stick : Stick: Sq. meters. | Kilograms.| Kilograms. 
Meters. Meters. 


1.52 1.52 a 2. 1.07 0.4 0.37 

8: 1.83 h 1.53 0.7 0.44 
2.13 : 2.00 Pet 0.55 
2.74 : y 3.30 1.8 0.55 


These dimensions were originally expressed in English measures, the designation 
of the kite being the length of the central stick in feet; this explains the occurrence 
of odd fractions of a meter in the columns containing the dimensions. 

The kites described above flew in winds averaging between 5 and 18 meters 
per second at the ground, and at angular altitudes of 55 to 65 degrees. At a velocity 
of 10 meters per second, the average pull on the line was 5 kilograms per square 
meter of total surface. The improvement in this form of kite has been chiefly 
in the pull, the angle having increased but little. The pull of the kites con- 
structed at the beginning of the experiments averaged scarcely 2 kilograms per 
square meter in a wind of 10 meters per second, or less than half that exerted by 
the improved kites. 

Kites that become distorted and fly at a tangent to the mean direction of the 
wind can usually be corrected by tying a short piece of string diagonally across the 
side toward which the kite flies. The position of such a cord is shown by the dotted 
line, F, in Plate III. Figure 17. The effect of the string is to change the form of the 
cloth surface, flattening it so that the wind has greater influence upon it, and thereby 


restoring the balance so that the kite will fly well throughout its usual range of 


58 BLUE HILL METEOROLOGICAL OBSERVATIONS. | 
wind velocity. A common method of correcting a distorted kite is to tie a weight 
on the side opposite to that toward which it leans; but since this does not in the 
least alter the form of the surface, the balance of the kite is restored only when the 
wind velocity is between certain narrow limits; when it is higher or lower than 
these limits the kite sags to one side or the other, according as the effect of the 


weight is neutralized by the unequal pressure of the wind. 

An attempt has been made to adapt the Eddy kite to a greater range of wind 
velocity by making the surface so rigid that the shape of the kite would be retained 
even under great pressure. The edges of one kite have been made of wood and 
braced by struts so that they would not bend backward when flown in a strong wind. 
The dimensions of this experimental kite are the same as those of the 7-foot kite 
in Table XV. The cover is left somewhat loose that it may form over the central 
stick a side-plane a little wider than is usually allowed in the Eddy kite. This kite 
did not fly with any arrangement of the bridle in any wind, but after the rigid 
edges and the braces were removed it flew as well as any of the Eddy kites. This 
experiment proves that the backward bending of the edges below the cross-stick 
is one of the chief causes of stability in the Eddy kite, and one which cannot be 
dispensed with, and that, in order to obtain still greater stability, experiment must 
be made in other directions. 

By the addition to the Eddy kite of the special tail already described, greater 
longitudinal stability is obtamed. The strings bearing the cones are usually two to 
three times as long as the kites, and when but one cone is employed the diameters 
and the lengths of the cones for kites of various sizes are as follows: 5-foot kite, 
20 x 30 centimeters; 6-foot kite, 25 x 35 centimeters; 7-foot kite, 30 x 40 centi- 
meters; 9 foot, 40 x 50 centimeters. These dimensions are only approximate, because 
considerable variations may be made without much effect on their flight. The cones 
are very useful; and in some cases, when the kites will not fly at all, the addition 
of the cone restores stability. One great disadvantage of tails of any kind is their 
liability to entanglement with the lines of other kites when flown tandem, which 
is sometimes the cause of great annoyance. For this reason, the kites having tails 
are almost always placed at the end of the main line. 

5. The keel kite was designed by Mr. Clayton in December, 1896. It consists 
of a single surface, either flat, curved, or composed of two planes at an angle to each 
other. The sticks preferably cross at a point about 20 per cent of the length of the 
central stick from its top end. In front of the kite, and forming a part of the 
central stick, is a vertical plane, the width of which is usually about one third 
that of the kite. Its form and the manner of attaching the bridle are shown in 


EXPLORATION OF THE AIR BY MEANS OF KITES. 59 


Plate III. Figure 23. The lower part, A, of the bridle is elastic, and when the 
wind is strong this elastic part stretches and allows the angie of incidence of the 
kite to the wind to become less, thus slightly decreasing the pull without decreas- 
ing the stability. Designed originally for use in extreme ranges of wind velocity, 
this kite has proved quite successful, flying well in winds of 5 to 25 meters per 
second, at an angular height equal to that reached by the other kites under more 
favorable conditions. The chief defect of this kite is its Hability to distortion, 
and also the difficulty of restoring it to a normal condition after its symmetry 
has been disturbed. The results obtained with the keel kite, however, are far 
from discouraging, and experiments are being made with a view of removing these 
defects. . 

6. The first Hargrave kite built at Blue Hill in August, 1895, had the same 
dimensions and weight as the smallest of those described by Mr. Lawrence Hargrave 
in Engineering for February 15, 1895. It is shown in Plate I. Figure 1. The 
dimensions of the kites of this pattern given in Table XVI. are thus measured in 
Figure 1. A B is the width, and BC the length of the kite; AZ is the depth, 
and # G the width of the cell. The cells consist of single bands of cloth stretched 
over rectangular frames of spruce wood; these are mounted on a central truss or 
spine, the sticks of which are heavier and stronger than those forming the cor- 
ners of the cells. The edges of the cells are stiffened by a cord in the hem of 
the cloth, but are not unyielding. This kite flew with remarkable steadiness, but 
at a rather low angle compared with that attained by the Eddy kites. The prin- 
cipal causes of this were the flapping of the cover, which became loose while 
the kite was flying, and the lack of rigidity of the frame. Mr. Clayton, who 
made nearly all the experiments with the Hargrave kite, has greatly improved 
this kite by making it lighter and more rigid than the original. The details of 
the improved kite are radically different from those of the original, and, to dis- 
tinguish it from the others, it is called the modified Hargrave kite. Two experi- 
mental forms are shown in Plate I. Figure 1 shows the original Hargrave kite. 
It was necessary to alter the construction of this kite, for the following reasons. 
1. The pressure of the wind upon the diagonal braces in the cells caused the kite 
to fly at a comparatively low altitude. 2. The cells were not rigid and were easily 
distorted. 3. The absence of connection between the outer ends of the cells allowed 
the kite, when flown tandem, to catch on the main line. When thus caught, it 
could not be dislodged until drawn to the ground. 

Plate I. Figure 2 shows one of the earliest attempts to improve this kite, and 
this is the simplest of all that have been tried. The frame is composed of but 


60 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


eight sticks, — four extending longitudinally through the corners, and connecting 
the two cells; and four extending diagonally across the cells, and secured at their 
ends to the longitudinal sticks. The defect of this kite is its liability to become 
distorted. The diagonal sticks easily bent under pressure on account of their 
extreme length. The extension of the longitudinal sticks through the entire length 
of the kite prevents the corners from catching on the main line when the kite is 
flown tandem; therefore this device has been retained in subsequent forms. 

A more complicated, but more efficient form, is shown in Figure 3. In this form 
the longitudinal sticks are supported by sticks extending laterally across the upper 
and the lower planes of each cell, and by short uprights at the side of each cell. 
A modification of this kite contains but one lateral stick extending through the 
middle of each cell, and supporting the longitudinal sticks by the short uprights. 
The objection to this form is, that all the strain comes upon the two cross-sticks, as 
in the kite shown in Figure 2. In another kite the cells were connected at the 
lower corners only, but this resulted in loss of rigidity, and no others of this pattern 
have been made. 

7. The Hargrave kite as modified by Mr. Clayton is shown in detail in Plate III. 
Figures 24, 25, 26, 27, and 28. The chief deviation from the original Hargrave kite 
is the elimination of the central truss or spine, and the extension of the sticks at 
the corners of the cells through the entire length of the kite, thus rigidly con- 
necting the two cells and rendering it impossible for their relation to each other 
to become disturbed. This method of construction greatly simplifies the kite, because 
in the new kite four long sticks.are made to serve the purpose of the ten in the old 
kite. This method has been used in all the kites made since August, 1895. In the , 
first kites of this improved form, made in September, 1895, the diagonal pieces 
(D, D, in the old kite shown in Plate I. Figure 1) are replaced by a single straight 
bar extending across each cell and supporting the four corner sticks by an upright 
at each end. The cover is laced on, and its tension is adjustable. The sticks at 
the corners of the kite are united by the device shown in Plate III. Figure 27. 
Two thin strips of aluminium of the same width as the sticks are bent to an angle, 
and secured to the sticks A and B, which respectively form the horizontal and the 
upright sticks of the cell. The longitudinal stick, C, passes through the square 
opening or slot formed by the ends of the other sticks and the outer aluminium 
strip. The angular pieces are secured to the sticks A and B, by cord or by small 
bolts, as shown in the drawing, and the stick C is fitted smoothly into the slot. 
The kite can be easily taken apart by sliding the stick C out of the slot. This 
new kite is much lighter and more rigid than the one first constructed, and several 


2a 


EXPLORATION OF THE AIR BY MEANS OF KITES. 61 


have been made for use. The angular altitude reached was lower than that attained 
by the Eddy kite, and further improvement became necessary. The fluttering of 
the cloth cover in the wind was probably the cause of this defect, and in the next 
kite constructed the edges of the cloth were stiffened by thin sticks of lenticular 
cross-section, which present but little surface to the wind. This method of construc- 
tion is described by Mr. Hargrave in the Proceedings of the Chicago Conference 
on Aerial Navigation, in 1893, and it was used by Mr. C. H. Lamson in a large kite 
built during the summer of 1895. (See articles by Hargrave and Lamson in Means’s 
Aeronautical Annual for 1896.) Professor Marvin has also pointed out the advan- 
tages of stiffening the edges of the cells in the Monthly Weather Review for May, 
1896. The details of one of the cells of the new kite are shown in Plate III. 
Figure 26. The angular connection shown in Figure 27 is used to connect the 
sticks at the corners, A, Bb, C, D, (Figures 24 and 25,) and, in order to render 
the frame rigid, wire guys, /’, /, are stretched diagonally across the cell, connecting 
the corners. These wires are placed on every side of the cell, those on the vertical 
sides extending tlie entire length of the kite. The dotted lines show the positions 
of the sticks and wire guys covered by the cloth. The cloth is secured to the 
sticks by paste or by sewing the cloth around them. The structure previously 
described is much more complicated than the original Hargrave kite, and slightly 
heavier; also the time required to construct it is much longer than that required 
for any of the other kites. The advantages of the several modifications are great, 
because the new kite will fly at a very high angle, which is nearly, if not quite, 
equal to that attained by the Eddy kites; while the pull and the stability are not 
impaired. These improvements led to the more general adoption of the new form 
of Hargrave kite. Since the dimensions of the kites may be varied considerably 
without appreciably altering the stability, it is probable that a still more efficient 
form may yet be devised. Experiments on wind pressures have shown that the 
pressure upon an inclined surface, such as a kite, is always greatest on the front 
end; and with the object of arranging the rear cell so that it should not be shel- 
tered by the front cell, a kite was built with the two cells separated by a space of 
more than twice the width of their cells. Since no appreciable advantage resulted 
from this, the rear cell of the next kite was made about one tenth wider than the 
front cell, the two cells being separated by a space a little wider than the rear cell. 
‘As a result, the kite attained the highest angle reached by any of the Hargrave kites ; 
and, since this is the chief result desired in kites for reaching great elevations, all 


the Hargrave kites are built at present according to this plan. The dimensions of 


the Hargrave kites employed in the flights are given in the following table. 


62 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


TABLE XVI. 


ELEMENTS OF THE HARGRAVE KITES. 


Secti Sticks : T Weight per 
Width of | Length of | Depth of | Width of Lifting eee Millimeter | Wotune of Sq. Meter 


Kite: Kite: Cell: Cell: Surface : Kite: of Lifting | References to Drawings. 
Meters. Meters. Meters. Meters. |Sq. Meters. Kilograms,| Surface : 
Lateral. |Longitudinal, ‘| Kilograms. 


152 | 1.80 | 0.57 | 0.58 | 858 | 240 320 2.47 | 0.69 | Plate I. Fig. 1. 

1:12} (9.82) -} 0.46 0.41") 1.84 | ’g00 200 1.56 | 0.85 | Plate I. Fig. 3. 

0,91) 5 Lous) Oates i tee 1.48 40 80 0.82 | 0.55 |) Plate IIL. 
OF 1B 12 il 80.46 PO 40a 2327) 110 110 1.64 | 0.77 |) Figs. 24 to 28. 


The lifting surface is assumed to be the total surface minus the side planes. The 
sticks have a rectangular or an elliptical cross section. 

Several kites of each of the sizes given above have been made, each frame 
being slightly different from the others. All these kites are very stable, and fly in 
recorded wind velocities of from 6 to 20 meters per second. ‘Thé angular altitudes 
reached by the first two kites average between 45 and 55 degrees, and those 
reached by the last two average between 50 and 60 degrees. The pull in a re- 
corded wind of 10 meters per second averages about 5 kilograms per square meter 
of lifting surface. The bridle used is shown in the Plates. 

Method of Testing Kites. —Since the use of kites for elevating instruments is to 
reach considerable heights, the kite which attains the highest angular altitude — 
other things being equal — is best adapted to such use. Another requisite of nearly 
equal importance is stability, without which the use of the kite is limited only to 
the most favorable conditions. To these may be added two other factors, — sim- 
plicity and durability. All these considerations are sought for in the kites employed 
at Blue Hill. . 

The method of testing kites is to fly them with a short line, usually 50 to 100 
meters long, and to make frequent and regular observations of the angular altitude 
and of the pull. The instruments employed are an alt-azimuth or a surveyor’s tran- 
sit, and a spring balance. Tests are usually made under widely varying condi- 
tions of wind velocity, in order to determine the fitness of the kites for use in all 
velocities. By these tests, the kites flying at the highest angles and through the 
greatest ranges of wind velocity, and those exerting the greatest pull, are easily 
selected ; or, in other words, this method of testing shows the relative capacity of 
the kites for performing work, which, in this investigation consists of raising a 


meteorograph of known weight under varying conditions. 


EXPLORATION OF THE AIR BY MEANS OF KITES, 63 


The estimate of the usefulness of the kite should also include some consideration 
of its durability, and of the time necessary to keep it in good condition. The mate- 
rials used in constructing kites are more or less fragile, and are easily affected by 
atmospheric changes, especially when they are under strain. Therefore simplicity 
of construction should be given first consideration, At Blue Hill the simpler forms 
are preferred, and no complex structures are employed unless there is a decided 
advantage to be gained by their use. 

Analyses of the forces acting upon kites are given by Mr. A. Samuelson in the 
Zeitschrift fiir Luftschiffahrt for December, 1895, and by Professor Marvin in his 
pamphlet, Kite Experiments at the Weather Bureau, published in 1896 by the 
United States Weather Bureau, Washington, D.C. 

Flights with the Meteorograph.—In flights with the meteorograph the kites de- 
scribed in paragraphs 3, 4, 6, and 7 were employed. Plate VIII. shows the appear- 
ance of two of these kites while flying. In any flight kites are selected with 
reference to the prevailing conditions of wind and weather. Usually, two kites of 
size sufficient to lift the meteorograph to a good angular altitude were used, allow- 
ance being made for possible increase of wind velocity with increase of altitude, so 
that the strain upon the line shall not much exceed one third of its tensile strength. 
The meteorograph is suspended from a ring at the junction of the two kite lines with 
the main line, as shown in Plate LV. Figure 32. Other kites are attached when 
permitted by the decreased pull due to the weight of added line. In Table XIX. 
are given the details of the flight of August 26, 1896, which show the observations 
usually made at the ground during a flight. 


METEOROGRAPHS. 


{ The recording instruments employed in this investigation are of the Richard 
pattern, lightened and modified to suit the exposure which is essentially different 


, from that of instruments mounted upon a fixed support, or lifted by a free balloon. 


he constant oscillations impressed upon the instrument by the motions of the kites 
upporting it, or by the varying pressure of the wind upon the instrument itself, may 
ause larger errors than are found in the record of the stationary instruments. Such 
rrors are due to flexure of parts of the recording mechanism, or of its supports. 
rrors due to sluggishness of the instrument or to friction are apparently smaller 
n the kite meteorographs than in the fixed instruments, because the oscillations of 
he former prevent the pivots or arbors from sticking. Errors are prevented as far 
s possible by mounting the recording mechanisms on rigid supports, by careful 


adjustment of the various parts, and by frequently cleaning the bearings, ete. 


64 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


Errors due to exposure of the instrument are not so easily corrected. The 
exposures of the barograph and of the hygrograph are not of great importance, 
because errors due to temperature or to the wind are much smaller than those due 
to other causes. It is sufficient to expose the sensitive parts so that a free circulation 
of air around them is secured. The suitable exposures of the thermograph and the 
anemograph are the greatest difficulties encountered. 

The results of the investigations of thermometer exposure by many authorities, 
and especially by Dr. R. Assmann, may be summarized as follows : — 

1. The bulb of the thermometer should not be connected directly with any part 
of the instrument exposed to direct sunlight. 2. It should be screened from direct 
sunlight by means of double walls, which are preferably made of non-conducting 
materials, and are insulated from one another and provided with a space between 
them through which the air can circulate freely. In these air spaces there should be 
no corners or angles liable to retain the air, and allow it to become heated. 3. No 
air that has passed over metallic parts of the instrument heated by the sun should 
come in contact with the bulb. 

The bulbs of the kite thermographs used at Blue Hill have been screened, as 
far as possible, according to the principles mentioned above. ‘The experiments with 
different forms of screens, described on pages 66 and 67, were conducted by Mr. 
Clayton. The several devices are there explained in detail, in order to show the 
process of development. / 

The exposure of the anemometer also requires very careful attention. When 
the meteorograph is suspended freely in the air, it is seldom at rest, but is moved to 
and fro, laterally and vertically, by the kites from which it is suspended, because 
they are influenced by winds of varying intensity. Also, the pressure of the wind 
upon the instrument itself forces it backward from its vertical position; and, since 


the wind is often quite variable, the instrument is caused to swing like a pendulun 


almost constantly. When the instrument is rigidly secured to one of the kites 
or to the line below the kites, any change in the angle of incidence or in th 
position of the kite alters the angle of the instrument with reference to the wind 
Such changes in its vertical angle are usually more permanent than any othe 
changes. In addition to these influences, that due to local changes in the direc 
tion of the air currents may be mentioned, though probably at high levels this i; 
not marked. Hence, in order to secure a uniform exposure, the instrument should 
be arranged so as to take its own equilibrium when suspended freely in the ai 
from one of the kites or kite lines. Then the angle of the instrument will remair 


nearly constant, irrespective of changes in position of the kites; and since a sing] 


EXPLORATION OF THE AIR BY MEANS OF KITES. 65 


suspension is to be preferred on account of safety, the anemometer which presents 
the smallest obstruction to the wind, and which is least affected by changes in ver- 
ticality or by changes in direction of the wind, is best adapted for a kite meteoro- 
graph. All anemometers requiring a vane to orient them are unsuited to such use 
because even when fixed in a vertical position they tend to under-register if the 
horizontal direction of the wind is variable; moreover, when these instruments are 
suspended from the kites, the effect of sudden gusts in disturbing their verticality 
would probably cause them to register still less. One advantage of such instru- 
ments is that they are more easily protected from injury than others, and possibly 
a good method of exposing an anemometer of this pattern may yet be devised. 
Several devices have received consideration, but have not yet been tested. The 
Robinson cup-anemometer is independent of changes in the direction of the wind, 
but is affected by changes in the verticality of the instrument which tend to decrease 
the registration, and perhaps by the pendulum-like oscillations of the instrument 
which may cause it to over-register. The exact effect of such oscillations has 
not yet been determined, but the records from a cup anemometer suspended from 
the kites at the same height as the Observatory anemometers indicate that at 
moderate velocities this effect is unimportant (see page 94). This form of ane- 
mometer is quite simple, and, being easy to construct and to keep in order, it has 
been adopted for current use. Its principal defect is that the cups, which are 
placed below the box containing the recording mechanism, are thus subject to 
damage by collisions with the earth, trees, or buildings. 

In Plate VIII. is a photograph of the first Richard thermograph, modified by the 
writer for use in 1894. The base plate consists of a plate of hard rubber stiffened 
at the sides by wood. The other parts were made chiefly of aluminium in order 
_ to obtain the requisite lightness. The recording mechanism, being of the well 
known Richard pattern, requires no further description. 

In Plate VIII. also are two photographs of the baro-thermo-hygrograph made 
by M. Jules Richard, and employed since March, 1896; one showing the details of 
the mechanism, and the other the instrument with protecting cage and suspension 
cord attached. The instrument, complete, weighs 1.3 kilograms. A cut and descrip- 
tion appeared in La Nature of February 8, 1896. 

Plate IV. Figure 30 shows the details of the thermo-anemograph employed from 
November 16, 1895, to June 22, 1896. The pen-arm, M, bulb, A, and adjusting 
screw, LZ, form the recording mechanism of the thermograph. The cups, A, A, and 
pindle, B, of the anemometer, are supported by the tube, C, which fits into a 
D, secured to the base plate, JV, of the instrument. The disk, P, at the 


66 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


top of the spindle, is of hardened steel, and is supported by steel balls contained in 
the cup £, which is also of hardened steel. The bearing at the lower end of the 
tube C is of brass. A thumb-nut, D, prevents the cups from dropping off the 
spindle when in the air. The cups are 2 inches (50.8 millimeters) in diameter, and 
the distance between their centres and the centre of the spindle is 3.36 inches 
(85.5 millimeters). Assuming that the cups move with one third of the true velocity 
of the wind, 1,000 rotations of the cups are made during the passage of one mile 
of wind. The speed of the cups is reduced by the worm-gearing, /, G, and H, so 
that one rotation of the wheel H is made during the passage of five miles of wind. 
Into the face of this wheel are inserted five pins, against which the lever J rests. 
This lever is raised successively by the pins as the wheel rotates, causing the arm 
J, which carries the recording pen, to make a short vertical mark on the record 
cylinder, O, for each mile of wind which passes the cups. In Figure 31 is shown 
another arrangement of the ball bearing at the top of the spindle. In this, the 
working parts are all below the base plate, WV, of the instrument, and are thus pro- 
tected from dust or injury from other causes. The speed of the paper on the drum 
is four centimeters per hour. All the parts except the spindles, the cup arms, and 
the bearings, are of aluminium, and the entire instrument weighs 1.2 kilograms. 
The method of suspending this instrument from the kite line is shown in Figure 82. 
The lines £, B, and C show respectively the main line and the two cords leading 
to the kites. From the ring at the junction of the three lines extends a short cord 
(usually less than four meters long) the lower end of which is secured to the instru- 
ment. The heavy parts of the instrument are placed near one end, and the point 
of support is placed at the same end. A fan or sail, A, extends upward from 
the upper side of the other end of the instrument, and is equal in area to the end 
of the instrument below the point of suspension. Thus the pressure of the wind is 
exerted equally above and below the point of suspension, so that when the instru- 
ment is forced backward by excessive pressure it still retains an upright position. 
This instrument and the method of suspension were designed and constructed by the 
writer. 

Figure 33 shows the first method of screening the bulb of the thermo-anemograph. 
The casing, S, of the instrument projects on all sides to a distance of six centimeters 
below the base plate, V. The bulb, A, is secured directly to the base plate and is 
screened from direct sunlight by the projecting casing. While no direct sunlight 
can fall upon the bulb, the air in the enclosed space surrounding the bulb is lable 
to become stagnant, and, through contact with the casing, to be heated, thus causing 


the instrument to record much higher than the true air temperature. 


EXPLORATION OF THE AIR BY MEANS OF KITES. 67 


The next experiment was to cut away the projecting edges of the casing, and to 
surround the bulb with a tubular screen, R (Figure 34), which is secured to the base 
plate, VW. This screen, while providing a free circulation of air and sheltering the 
bulb from sunshine, is subject to heat conducted through the base.plate to the bulb. 
The bulb used in the thermo-anemograph is not so sensitive as the bulb in the 
Richard meteorograph; therefore, on receipt of the latter instrument, in April, 1896, 
subsequent experiments were made with this instrument. The screen first tried on 
this instrument was a bag of white muslin slipped over the cave and projecting 
slightly below the level of the bulb. The position of the lower edge of this cover 
is shown by the dotted line G, in Figure 35. This device was one of the worst 
tried, because the air confined in the cover rapidly became heated much above the 
air temperature. 

The last device tried is shown in Figures 35 and 36. In the top of the cage 
surrounding the mechanism are two strips of varnished cloth, A and B, with a 
space between them 8 centimeters wide. Under the strip B, and on each side of 
the bulb D, are narrow strips of cloth, C, C, the ends of which are tied to the 
front and the rear of the cage. These strips are separated from the strip B by a 
space 2 centimeters wide. A fifth strip, /, protects the rear of the bulb from 
direct sunlight. These screens protect the bulb from sunshine and allow the air to 
circulate freely between the screens and the bulb; moreover, the strips of cloth, 
being non-conductors of heat, do not transmit to the air around the bulb any heat 
from the metallic casing which is exposed to the sun. This device, although not 
considered perfect, is the best that has been tried thus far, and records made by 
the meteorograph when in the sunshine agree closely with those of the thermograph 
in the standard shelter of the Weather Bureau (see pages 92 and 95). 

In addition to the instruments already described a small baro-thermograph was 
lent by Professor 8. P. Langley, Secretary of the Smithsonian Institution, and was 
employed in a few flights. This instrument was made by M. Jules Richard for use 
in balloons at great heights. It is well made, very compact, and weighs but 0.8 
kilogram, which is less than any of the instruments employed in the kite experi- 
ments, The scale-divisions of this instrument were, however, entirely too small for 
use in the kite experiments. 


Note. — November 1, 1897. The experiments described having indicated that the exploration of the air with 
kites may be extended to greater altitudes, and prosecuted under a greater variety of conditions, preparations have 
. been made for the continuation of the work. To facilitate the use of a greater length of line under long continued 
strain, a new windlass with a strain-pulley controlled by a steam-engine of two horse-power has been constructed since 
February, 1897; also a number of important modifications of the meteorographs and accessory apparatus have been 
made, and tests of some new forms of kites are in progress. On October 15, 1897, the meteorograph was raised to 
a height of 3,379 meters above the Hill, or 3,559 meters above the Valley. 

| 


68 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


Il. — Resuttrs From THE Kire METEOROGRAPHS AND SIMULTANEOUS RECORDS AT 
THE GROUND. 


TABLE XVII. 


AIR TEMPERATURE AND WIND VELOCITY. 


oF ae 7 i ei Sa. ae 
Date con Air Temperature baie Wind Velocity Date re Air Temperature Sse Wind Velocity 
and Po| Bos? Pic and spat soe #5 
Hour, | 25 Ss at on in gm at on Hour. | 25 Bes at on in es at on 
a2) 4aeF Kite. Hill, | Valley.| 4S | Kite. | Hill. mea | ee Kite. Hill. | Valley.]| &S | Kite. | Hill. 
1894. 1895. 
Aug. 4. meters. oF, OSES OF. | p.ct. |m. p.s.|m.p.s.} Aug. 20. meters. OF, PK: OF, | p.ct. |m. p. s.| mp. s. 
2221 ake LO tan Ooo MOO: OMmOScon me iE 4.9 f11:204 452 | 62.3 | 68.8] 70.0} 48 | ..1| 8.5 


63.4 | 66.8} 69.0; 69 | .. | 4.9 J11:254 342 | 63.8 | 68.8] 70.0) 48 | .. | 8.5 


2 
2:41 Pp). .| 283 1 
3:08 Bh ale Soe i) G4en 7 O92 a7 eG Wh Sab Souk ial eS Oar mG SoM eoueL Om) t. ,. /Mmece 
3:10 P). .) 898) G47.) 69.40 77) 64), 2 1: 5.4 [11:47 «118 Sia eee eee e348 |. . Mee 
4:37 Pk.) 4807], Od.0 | OGL s 1-41 680) 2 A 15.84) 0:1 Ze BIS some Oteem mOsm StonmO OM! 9... imieO 
4:54 p |). % | max. | 64.1 | 69.7.) 72:3) 62}. . | 5.4.1 0:19). 48805) 63205) 67,9) 692249 ) . . eG 
5:03 P|...| 616°) 64:3) 69.4) 72.3762 | 2. | 6.7 | 0:54 P7o1 S83 bb OTs OOte ooo | . . laaG 
5:05 p|. «| 509 | 64.4 | 69.9) 72.2) 62°) ..1-7.2 | 1:30 he). 11342 1.64.8 ).68,6169.0) 48°) .. (10s 
Aug. 15. Aug. 22. 
1:30 Pp). .}| 318 | 72.2 | 72.7) 77.4) 73 | ..| 89] 5:45P]...| 2381] 64.2 | 66.4) 64 44); ..] 4.5 
1:52 Pp]. .| 386 | 71.0 | 72.9) 77.4) 74) .. | 8.0] 5:55P). .| 368) 62 66.0 | 68 Ow. '. |MeesO 
8:28 P|. .| 488 | 67.5 | 71.1) 73.8) 76 6.7 | 5:58P]. .| 3884 } 61 65.8 | 63 46). . | 74.9 
3:30P|..| 441 | 67.6 | 71.0} 73.8] 76 6.3 | 5:59P]. .| 876 | 61 65.7 | 62 AGH». . (ARS 
4:03 ep}. .| 300 | 69.8 | 71.3] 74.1] 79 8.9 | aug. 23. 
4:18 Pp]. .| 339 | 69.4 | 70.3] 72.7] 79 8.9 | 5:40P 327 | 71.5 | 74.0} 72.5 
4:20 Py. 31-238) /69.6°) T0211 72:5 79 9.4 Aug. 24, 
Aa 10:50] 5| 297 | 76.4 | 79.3] 81.8] 72 7.6 
July 23. 11:30 4] 40} 805 | 77.6 | 82.3) 84.4] 65 8.0 
3:20 P|]. .| 540 | 69.0 | 74.5] 77.0) 49] ..] 7.2] 0:05r) 6} 890 | 79.8 | 84.5) 85.9) 62 8.5 
July 29. 0:20P) 6| 441 | 77.8 | 84.2] 86.5] 66 7.6 
11353 a}. «| 268 | 73.3.) 74.8) 76.6 | 47 6.7 | 0:46P|12| 540 | 77.5 | 85.7] 87.3| 61 8.5 
11:54a/..| 278 | 73.0 | 74.8) 76.8} 47 6.7 | 1:08P). .| 483 | 77.7 | 84.3) 86.9) 64 8.5 
0:37 P|. .| 543 | 71.0 | 76.5) 77.4) 46 7.2 | 2:06P|. .| 306 | 78.0 | 83.8] 86.6] 68 10.3 
0:38 Pe]. .| 484 | 72.1 | 76.5] 77.4] 46 (oe eee 
O:44 Py). 2} 512 | 704 | 75.3) 77.0) 46) 0.0) 6.7 [22:59 P) 61 BBT e770) Fre iee.O1ne0 6.3 
1:23. P)...,| 686 168.3). 79.6 )978.0) 46.) 5°. | 6.7.]- 8:09 Bio Ty 286 wey G.oulerecoy eel ees ue 
Pons. 3:21p| 6| 373 | 75.1 | 78.0] 78.6| 44 8.0 
ID15 Aj. | 497 1 TE TAO T4 8) 694...) 7.2 | 3:32.P) Cee ba aerosol r odeaD 7.6 
11:184| 2 | 590 | 70.0 | 74.0).74.9) 58 | ..| 63] 3:46P]. .| 449 | 71.8] 76.4] 76.6| 47 fey? 
11:344| 4 | 464 | 70.4 | 74.9] 74.8) 56] .. | 8.0] 3:57P| 9} 546 | 68.5 | 75.9] 75.9) 48) .. | 8.0 
0:18'R1 3 ‘| 350°]: 10-89- 72.717 73.6 59) 86.7 1° 4:39 By Le O27 MGT Ta Sea bd L*.. 5 | Bede 
:54P) 5 | 422 \ 71.4 74.6) 75.0) 57] 9. |. 5.8.) 4:55 2 | 10 6aimoe-.en) P27 yeas |. oes 
2:27 Po | O70 4070.0 | 76.24 768) 45 102 2) G7] 5305 BO eGtaie.0 72) eras 0) |... ines 
8:00 Pp} 2 | 590 | 69.0 |) 74.21°76.5)' 44710. 2 | '-8.5i] 5:10)? 4 6520) Chive) 719 (729-61). . |e 
S:02P) 1) 474.4 738.38) 74.7) 760) /45 7°... |0 9.81 6: 25h) Si eoinieGo aa On ieee ed Oo | .\. meee 
3:28-p.| 1 | 634 |°67.6.) 73.6) 75.5) 47 1 2.4 63] 5:32 P) Sy ostor Geo 70.0" 7144 66} . .. \aeo 
auntso, 5:37e]. .| 501 | 67.8 | 69.7| 71.0| 67 | ..| 4.9 
11:09} 1 | 310 | 64.7 | 68.8) 69.5) 48] ..| 76] 541P]. .| 421 | 68.5 | 69.6) 70.8) 69 | ..| 49 
£11:16.a | 2°(°295 | 64:5-).69.0) 7050) 48°)... | 7.6 (05:46 P|) Sega ensos Ba OF Sl TOO) fee 
111:184| 2 | 373 | 64.4 | 69.0] 70.0] 48 7.6 | 5:52 Pp]. 5) 268 } 69.6) 69.0) 70.2) 70 | .. 4.9 


EXPLORATION OF THE AIR BY MEANS OF KITES. 69 


Air Temperature Wind Velocity Air Temperature £ | Wind Velocity 


Date 
and 
at on Hour, 


Kite. | Hill. 


Interval in 
Minutes. 
Altitude 
Humidity 
on Hill. 
Interval in 
Minutes. 
Altitude 


above 
Valley. 


at on 


on in in 
Kite. Hill. | Valley. 


at on 
Kite. Hill. | Valley. Hill. 


1895. 1895. 
Aug. 27. Sie ct, |m. p. &.| M. p. 8. Nov. 16. : : OF, . ct, |m. p. 8.| M. p. 8. 
9:15 Pp TOAST to ||) oe) oO 5 a os 
2:25 p 79.2 | 7 a Det 4:40 p 5.4 
9:53 le 79.6 36 nary ° Nov. 17. 
3:16 Pe MO Ge AF y 8:46 4 
3:40 Pp TOBA 65 vow. aC 8:56 A 
4:00 P 79.1} 6 ae : 9:32 a 
4:37 P 77.0 5 ois 8 | 9:45 4 
4:59 P 75.8 | 6 ot: : 9:57 A 
Aug. 28. 10:03 a 
8:50 P 10:15 4 
4:00 p 10:26 a 
4:35 p 11:044 
4:45 p Noy. 18. 
4:00 2 3:13 P 
5:10 e 3:42 Pp 
5:20 p ARGO h gel. 
6:24 ep 4:25 p 

J 5:38 P 4:30 P 
5:50 P 4:01 P 
5:59 P Nov. 19. 
6:02 P 2:25 P 


° 
ry 
bee 
y 


-1 
bo OD 


~I-1 4 
pre ees 

Hm Os 4 Oo & tO” 
aa 

oO 


-1 

-l 
Was 
ODO OS Ove” 


oo 
-1 


8.5 


te 


~ 
eo) 

I 
at seo = 


“I 
cornet 


bo 


~ 
“I 
5 
~I bo bo 
Omem & A ocd > 


— 
ae 
bo & 


—~1 me to 
“I bo 
co | 


“1-1 © © 
(0) 


“1 4] 
or oa 

Satie TS ee 
~ Ww Oo be 


HM ao 
fe eae 
Tb Ot 


=I 


I 
Le ee ee ST 
oO 


ee 


I =] 


. 
~ 


“1 
SESS) OS 


ia 


or 
© te 
-1 
io) 


oe 


Aug. 31. 2:40 P 
0:05 Exiee 8. a: : ( ae ‘ 2:56 P 
0:17 PRWeee oo ; : 3 sa 2| 3:47P 
0:24 Pp 6.6 De : acts : 3:56 P 
0:40 POtes ) fe 3 A ) ace . Nov. 20. 


0:45 p 1:23 P 
0:49 p 1:30 P 
0:57 P Nov. 23. 
Sept. 21. 11:47 a 
1:27 Pelee 2 | 88. 9} 91. Af ad “7 | \Alnlesyaye 
1:41 Pe js a) 39.9} OL. f oe : 0:05 p 
1:48 Paes Jeg 89.8} 92.0 i Sua ‘ 0:34 p 
9:08 aE vo. S ‘ by pe ‘ whe Fi Nov. 25. 
2:18 P 83 | 84.: 9, 92. AY. : Piya 
2:27 P : 89, 92. : me BA | ISSEY 
2:44 Pp Ne oY! 0,2 : & bys 6 [11:444 
2:53 P ; 39). 92. 4 “a 6 112:00 a 
3:00 PaeelOzo: |, SL. .o| 92. sa ‘ 0:10 Pe 
3:11 P 36 ; ! 91. eae ; 0:24 p 
4°10 Pee ; Fie ate F . ; 0:25 P 
Nov. 16. 0:33 P 
DOD 2 Pome S foi| tte sh 5. : 1:00 Pp | 
2:39 P | pio Wace Cee ite One » | 6.7 8.0 | Nov. 97. 
3:04 Paleeninac 2 elt OCR ee 1.3 9:37 A 

13:42 Poles PELE fe lente ts 3. 10:03 a 


ao 
Ov or 


(or) 
or 


be | 
—_ 


~I 1 
“10 Bb 


Io no ao 
“1 


=] 


1 


— 
- © 
I 
oo wf 


= 
oo co 
oO wo 
~| © 


— oF 
CoO m 


70 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


Humidity 
on Hill. 


Air Temperature Air Temperature Wind Velocity 


Date 
and 
Hour, 


Date 
anil 
Hour. 


Wind Velocity 


Interval in 


Minutes. 


at 


at on in on 
Kite. | Hill. 


Kite. Hill. | Valley. 


at on 
Kite. Hill. 


at on in 
Kite. Hill. | Valley. 


| Altitude 
above 
Tnterval in 
Minutes. 
Altitude 
Humidity 
on Hill, 


Valley. 


1895. 1896. 
Nov. 27. erg.| OF. ‘ or: . |m. p. s.|m. p.s.} Jan. 12. Bie, ode 251 Cha 
10:43 4 S| Sei! A} 41.5 7.6) 8.9 |10:47 4]... 2300 23.00 13:8 
11:03 a 330) by, 42.3 SoleOr 6} L000 cage OA ome oem Ase 
11:15 4 ‘ 35.4 | 88.8] 42.7 ue ater | welansela: 
11:38 095 | 39.3 | 39.3] 43.0 sel se [yee 26.3 
2:59 P 24.7 
3:08 P 5 24.1 
3:18 P 29:9 
SPAWN || 22.8 
3:30 P 21.9 
3:32 P 19.9 
3:41 P 19.6 
Waits 10 195 | 400 | so] 43. | 242 108 | 207 | 262 
10:13 4 818 | 87. ).8| 42.4 ae eel eel ers 
seat a ets Cee 4:06 P 21.8 | 26.5) 27.9 
Pere sear eth seers 4:13 P 23.8 | 26.3| 27.6 
oa ee: ; A 4:20 p 9b aL des 
11:39 a 

Jan, 17. 
Dee. 9. 11:364 6 |) 30)49| (34.4 
9:12a] 5} 192 “ -- | 4.9 111:45 41 6) 42 i .6| 34.3 
9:22a] | 26 8. . -- | 5.4 112:00 4 ‘ 5| 34.4 
9:32 4 8 | 18. 8. “ ..| 49] 0:07 2 pe 5| 34.6 
946A) § ( 3) 21.6 .- O:15P|.. 8 | 30.6] 84.7 
9:56 A B18 | 25.2 | 18.5) 21. a 0:17 Pies 5! .7| 34.6 
9:59 a]. .| 268 | 21. 8.6} 21. “i 0:22 P|. .| 26 : 8] 34.6 
EQ 002A ne ee 5 20. . ‘ o Jan, 18. 
Teenaa, 11:06 4 
9:524| 12 ae Baie ee meent Ayia | 111t aee 28.1 
10:31 4 482 | 18. Darilegs. : 4] 3:22P 30.2 
3:42 P : ; 27.3 | 29.9 

Dec. 12. P ‘ 
10:10 4 |13} 195 6 - , f d 3:51 P 
10:30 a | 15} 299 : d 6} 6! 5 | 4162 
10:45 wil ra) 299 tain € 5 | #19P 
4:26 P 
4:39 Pp 
Jan. 27, 
2:20 P 
2:39 P 
3:00 P 
oe 
8:26 P 
3:33 P 
3:57 PB 
4:19 p 


Dec. 25. Jan, 28. 


A:-45 p| 1§ 4 ‘ 3 y : : 5:29 Pp 


Ss 
3 
(Pi 
= 8 
Crs 


LOW doa 
> 


w ow og 


te 
a | 


29.5 
29.3 
29.1 
29.0 
28.8 
28.5 
28.4 


28.2 


=I 
wim & 


bt be 
=I 


Noy. 28. 
9:47 A 2° 34. .0| 88.5 
10:10 A 320 | 34. 39.8 | 40.0 
10:30 A 3 a4. os l  4053 
10:48 a | 18} 362 | 36: 8.0 | 41.9 
10:55 ad -6), Be 37.3 | 38.1 | 42.0 


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Dee. 21. 
2:18 P 207 
2:26 P 282 
2:40 P 386 
2:56 P 
3:12 P 
3:30 P 
4:14 p 
4:96 P 
4:47 Pp 


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Dec. 26, 5:50 p 
4:05 P 302 eile : SO MeL Oke 6:01 Pp 


EXPLORATION OF THE AIR BY 


MEANS OF KITES. 


Date : #|o . Air Temperature a Wind Velocity Date s et Sa Air Temperature 2. Wind Velocity 
and ha| Bos ato and Ee| fos =i) — 
Hour. Se 2es at on in s7 at on Hour, £5 So8 at on _in a7 cat on 
se | ase | Kite. Hill. | Valley.) &S | Kite. | Hill. Bra | tee | Kite. Hill. | Valley.| HS | Kite. | Hill. 
1896. 1896. 
Jan. 30. meters oF; or, 2 p. ct. |m. p. 8.|m. p. 8. Feb, 23. meters oF. ory oF. |p. ct. |m. p. 8.| mM. p. 8. 
1:10 Per 95: | 28.8)" 28.7 | $2.0 |) 68) F680) | 38:15 pl. 601 | 40.9 | 42.1] 41.0} 47 9.4 
1:25 p.}12|] 867 | 25.6) 29.3) 32.7] 67| 7.6] 7.6] 3:45P/. .| 500 | 38.9 | 43.3] 41.6] 47 8.9 
1:47 P |12} 590 | 23.0} 30.0} 33.3) 65] 85) 6.7] 4:03 PRP]. .| 545 | 387.7 | 42.7} 41.7) 49 8.9 
2:10 p |11| 330 | 28.8] 31.0] 34.9] 62] 7.2] 7.2 | mare 
2:26 ep |}11| 195 | 31.8/ 31.8} 35.0] 61] 5.8) 6.7 ] 5:30 P|15) 192 ; A te hismee OOF |. 4,0 '| 4.0 
rae 5:50P]11| 264 | 30.8 | 31.2] 31.8) 61] 63] 49 
10:044] 3) 217 | 20 2014 | 24.2 | 7 : .| o:58 Pp] 4] 233 | 81.9 | 30.9] 31.4] 61 5.8 
1:16 Pe |10| 334 | 21.7] 25.9] 28.8) 85] 6.3) 5.8] 6:02P) 3} 228 | 32.4 | 30.8] 30.8] 62 5.8 
a a 6:05P|. .| 294 | 83.3 | 80.5] 30.5] 62 5.8 
5:29 e |16| 491 | 29.7] 33.9] 35.5} 49] 8.5] 7.2 | tar. 10. 
5:48 Pe | 6; 851 | 31.2) 83.3) 34.9) 50) 7.2] 7.2 | 2:05P] 10] 255 | 30.0 | 82.0) 34.6) 43 5.4 
Feb. 10. DOP OLD (Poll oo-OlLooco E42 4.5 
d:15P | 11) 883 | 26.5) 28.8) 31.3) 53)11.6) 9.4] 2:47P]. .| 428 | 29.0 | 33.7) 85.5) 42 |] ..] 4.5 
0:25P | 4] 545 | 23.7) 28.8) 81.1) 53)13.0] 9.8] 2:55e) 8} 269 | 30.4 | 33.4) 35.8] 42 | 10 4.5 | 
5:45 P |10| 342 | 26.5] 28.6) 30.9] 54/11.6] 8.5] 3:03r| 4} 33 30.3 | 33.1] 86.4] 42 9.8 
Feb. 12. Mar. 11, 
o:21 PRAIA B9I0 | 22.3)-25.4 127.9) 50)? 8.91 8.5 J 112038 4). .| 852 | 28.7 | 80.8) 32.2) 85 | . . | 10.3 
o:34P 110) 562 | 18.5} 25.1} 27.3) 50] 9:4) 8.9 [11:26 .4| 10] 323 | 28.2 | 30.5] 32.7] 86 |10.3| 8.9 
5:40 P 156) 578 |. 18.3) 24.8] 27.1) 50) 9.8] 8.5 ]11:33 4a) 6) 377 | 27.4 | 30.5] 32.7| 86 |10.7/ 9.8 
5:09 P | .6| 887 | 20.8) 24.5] 26.6) 50] 9.4] 7.6 111:504] 6] 452 | 25.8 | 30.6] 32.7] 86 pLOs 
Feb. 13. 12:00 4| 7| 573 | 24.0 | 80.6) 82.6) 87 11.6 
2:25 Pp.) 7] 311 | 28.3) 28.2) 31.4] 100) 11.6| 8.5 | 0:16 P| 15) 622 | 23.2 | 30.6] 32.0] 87 11.2 
2:30P | 6} 311 100 | 13. 8.5 | 0:35r| 6] 739 | 21.9 | 30.3] 30.8] 95 10.7 
Feb. 17. Apr. 5. 
4:20 ep | 8| 476 |—0.9} 2.6) 6.7] 44 9.4] 4:12P| 6] 267 | 38.5 | 40.7} 43.0] 40 | 8.9 10.7 
4:40 PRG IsO25 |.—4.5) 2:8) 6.5} 44 7.2) 4:26P| 8] 506 | 33.2 | 40.3] 42.3) 42 | 8.9] 8.5 
4:57P | 8) 825 |—0.2| 2.7| 6.0] 45 8.0 | 4:442] 5] 642 | 30.7 | 89.9] 41.0] 44 | 8.0] 9.8 
Feb, 18. 5:12P|10] 795 | 29.7 | 39.5] 41.8) 46 | 8.0) 9.4 
2:40 Pie) 300 | 15.9) 18.1] 21.6) 91 6.7 | 5:25p| 9] 697 | 29.4 | 89.4] 41.0] 48 | 7.6] 8.5 
2:49 PHieteage | 15.2) 18.7) 22.2) 85 5.8 | 5:50P|10) 753 | 28.3 | 38.3] 40.5) 50} 8.5) 8.0 
3:04P 110} 520 | 13.7] 20.7| 23.6] 82 10.7 | 6:01 P) -4) 778 | 27.1 | 37.8) 39.7| 51 | 8.9) 8.0 
3:21 Peco, | 16.6) 20:8) 23.7182 8.5 | 6:18 P| 8| 624 | 29.8 | 37.0] 39.0] 53 | 9.4) 8.0 
3:32P | 5) 198 | 20.0] 20.9) 24.0] 77 8.5 1 6:24r) 4] 548 | 30.9 | 36.8] 38.6) 54 | 9.4] 8.5 
Feb. 19. 6:35 r| 6] 376 | 33.7 | 36.6] 38.3] 55 | 9.4) 8.9 
5:14e | 8] 197 | 27.2| 27.3] 29.0] 61 (tee 
5:20 PWoieels | 26.0) 26.9) 28.6) 61 8.5 | 3:12P/] 6] 286 | 31.1 | 33.0] 37.0] 68 7.6 
Feb, 22. 3:27p| 8] 882 | 28.1 | 32.0] 35.8) 70 7.6 
4:45 Pea 348 | 20.7) 24.4) 27.2) 44 9.4] 3:33 P| 4] 472 | 26.5 | 31.8} 35.7] 70 7.2 
4:52P |.4) 494 | 17.2) 24.4) 27.1] 44 94} 3:36P). .| 540 || 24.8 | 31.8] 35.7] 70 6.7 
5:00 P |.4) 594 | 16.7| 24.3] 26.7] 44 11.6 | 5:25P/20| 778 | 20.6 | 31.1) 34.9) 71 6.7 
5:07P | 2] 687 | 16.3] 24.2] 26.4] 44 1G 8 
5:42 P 300 | 21.1) 23.4] 25.4) 46 10:3) ]) 9:22.4)15) 271 | 55.9 | 58.6] 61.6) 59 | 9.8) 11.2 
5:55 P 291 | 22.2) 23.3) 25.1) 46 8.9 | 9:304| 6] 360 | 56.0 | 59.1} 62.38) 57 | 12.1] 10.3 
aes 9:454| 4| 517 | 71.2 | 60.6| 63.6| 55] .. | 8.9 
2:50P | 6| 3857 | 39.7] 42.3} 40.9| 45 8.9 110:12 4 | 20] 680 | 71.5 | 63.1] 67.5) 58 | 13.4) 10.3 
3:03 P | 9} 473 | 387.9] 42.3] 42.2] 46 8.9 | 10:49 a} 84| 748 | 69.6 | 67.6|°70.7 | 48 | 14.8) 8.9 


=I 
bo 


BLUE HILL METEOROLOGICAL OBSERVATIONS. 


Air Temperature Air Temperature 
p 


Wind Velocity mate 
and 
Hour, 


Date 
and 
Hour. 


_ | Wind Velocity 


at in at on 
Kite. |) Hill. 


at on on 
Kite. Hill. | Valley 


Kite, | Hill. 


at 
Kite. 


Interval in 
Minutes 
Altitude 
Humidity 
on Hill. 
Interval in 
Minutes. 
Altitude 
above 
Valley. 
Humidity 
on Hill 


1896. 1896. 
Apr. 13. i Barty : . . |m. p. 8.) m.p. s.} Tune 19. 


11:05 4 115 9: 68.2 ? 2s 15.6 | 9.4 | 2:42 Pe 
11:16 4 005 | 67.1 | 70. 15.6| 8.5 | 2:44P 
11:38.4 954| 66.0 i 15.2| 8.0 | 2472 
0:08 P 586 | 70.0 11.6] 7.6 | 2:50 Pe 
0:18 P| 6 8.5 : 3:03 P 
0:29 p iA 8:07 P 
0:33 P 8.9 ; 3:ll Pe 
0:36 p 3:24 P 
0:38 P 3:34 P 
0:50 P 8:42 p 
1:10 P 8:48 P 
Apr. 18. 3:57 = 
4:57 p 312| 71. OV aoe 4] £06P 
5:30.71 thos 3.1] 64. TON 7.2 | eile 
Apr. 20. aout F 
4:45 Pp]. .| 5 0} 7 a tee bata 85.7 
148 Saas 4:05 p 85.7 
4226p |. . 34. 3] 85.7 
cere : Wie 4:30 P 3.2| 85.7 
5:05 P 5 9, : 3 sue oF ; oe 
mes | a IWeR palney eles 9 | 55P |. . 29 7] 85.2 
SiR Dc eee Leelee ; |, Bh 
ap Re - June 20. 
Hes eels | ; Pier eh Ozer ees [EbiB0 e ; 8) 82.4 
ie Se Nos aMy eran! OO ed A548 4 | 81.3] 81.0 
cae BSS 1) Le a eee ieee Vege-nar ae 1 60s an 2] 75.9 | 80.8] 81.8 
one (oor a Poa ee Aer. Nectd 9 | 80.7| 80.9 


° 
ty 


NAONDOwWW: 


Pa RC 
84.6! 86.7 
84.7 | 86.6 
84.7) 86.6 
84.6 | 86.6 
84.4] 86.6 
84.4} 86.1 
84.6] 85.9 
84.5} 85.9 
84.2} 86.0 
84.2} 86.1 
84.3 | 86.2 
84.0} 86.2 
84.5 | 86.1 
86.0 
85.9 


, |m. p. S| mM. p. s. 


1 
S 
> 
i>) 
= 


oo 
co 


ay] <7 

CO CO OH 
a 

2 09 

CO 


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Sil ee 
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wo 
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RtuScaiSs 


June 18, June 22. 
5:02 P 5 : ; : a -/ 7 3:41 Pp é 6) 83.6 
5:14 pe fl : : . . 4:10 Pp |; : ‘ 482.9 
O21 Pilea Ve : 9 300 -- | 4:31 Pp ) x ; 82.3 
d:40 P| § : ‘ : : : 5:15 pe | 1 o .8| 80.6 
OO UPAl pe 3 70. ; 82 as ys N35 8} 80.8 
6:00 P ‘ B Galenee ‘ : ay 5: ¢ Site : 80.5 
6:06 pP} ¢ 
6:16 P 
6:20 P|. 
June 19, 
FS UN SY lee 
2:39 p 


alee 


fay fen 


“IN DPW. 


=I 
= 1 


~] =! 
Som 
S 


(o>) 
Lo 
(op) 
io ¢) 


Notrs. — The second column gives the length of the interval, ending with the time given in the first 
column, that the meteorograph remained near the same altitude. The third column gives the mean altitude 
during this,interval. The fourth column gives the temperature recorded by the meteorograph at the end of 
the interval and at the time given in the first column. The eighth column gives the mean wind velocity 
recorded by the kite meteorograph during the interval given in the second column. The remaining columns 
give synchronous observations at the ground. 


EXPLORATION 


OF THE AIR BY MEANS OF KITES. 


73 


REMARKS. 


1894. 


August 4. Cloudy during the morning with strato-cumulus 
surmounted by a sheet of alto-stratus, but these began to 
break away about 2 p.M., though the sky continued more 
than half covered. ‘Temperature below normal. Wind 
WSW veering to W. 

August 15. The sky was covered with alto-cumulus and alto- 
stratus increasing in density, and it became necessary to 
draw down the kites on account of the approach of a 
thunder-shower from the west which reached the Obser- 
vatory at 5:14 pM. ‘Temperature normal. Wind SSW 

backing to 8. 


1895. 


Sky partly covered with cirro- 


July 23. Weather fair. 
Temperature above normal, but 


stratus'and alto-stratus. 
falling. Wind NW. 

July 29. At the time of the ascent cumulus clouds were pass- 
ing overhead and the wind was very gusty. As each 
cumulus approached the hill the kites rose rapidly, going 
up sometimes 100 or 150 meters in a minute, and falling 
as quickly. About 1:50 p.m. the cord broke, and three 
kites and the thermograph were carried about three miles 
in the next five minutes. They were recovered about 
6 p.m., and were found to be not seriously damaged. 
Temperature near normal. Wind W veering to WNW. 

August 19. Weather fair. Sky partly covered with cirro- 
stratus, and a few fracto-cumulus changing later to strato- 
cumulus. Temperature slightly above normal. Wind W. 

August 20. Sky partly covered with alto-cumulus, cumulus, 
and strato-cumulus, followed during the evening by 
cumulo-nimbus. Between 11:16 and 11:19 a.m. the kites 
rose rapidly towards the zenith, and reached the greatest 
angle above the horizon observed during the day (65°), 
and at the same time a small cumulus cloud began to 
form immediately above them. The observations indi- 
cate a rise of the kites of about 600 feet in three minutes. 
Cool wave on the 21st. Wind WSW. 

August 22. Clear weather during the flight except a few 
cirrus. Cumulus observed earlier in the day. Stratus 
formed during the night of the 22d. Very cool in the 
early morning of the 22d. Wind SW. 

August 23. Sky nearly clear at the time of the flight. Tem- 
perature rising rapidly. 

August 24. Warm wave. Sky partly covered by cirro- 
cumulus, alto-cumulus, and cumulus, followed during the 
evening by cumulo-nimbus. Wind SSW backing to S. 

August 26. The sky was clear, excepting a few cirrus and 
fracto-cumulus. Twice, after rapidly ascending currents 
which carried the kites upward, small cumulus clouds 
were observed to form near the zenith. Wind WSW 
backing to S. 

August 27. Sky partly covered with alto-stratus and alto- 
cumulus. Between 3 and 3:30 p.m. the kites along the 
line formed a well defined curve. 
from the SW, and the upper kites from nearly W. 


The lower kites were | 


August 28. Sky partly covered with alto-cumulus and cumu- 
lus. Very warm, followed by a cool wave on the 29th. 
Wind WSW. 

August 31. Sky partly covered with alto-cumulus and strato- 
cumulus. Wind S. ‘Thunderstorm in evening. 

Sept. 21. Exceptionally warm for September, the tempera- 
ture recorded on the 21st, 22d, and 23d being the highest 
in September for many years. The sky remained entirely 
clear excepting for a few cumulus during a part of the 
day. Wind W. 

Nov. 16. Sky partly covered with cirrus. A thermo-anemo- 
graph was used for the first time, and a record of wind 
velocity obtained. The record of temperature was lost. 
Wind W backing to WSW. 

Nov. 17. Sky covered with a sheet of alto-stratus, which was 
soon followed by nimbus, fog, and rain, Wind SE. 

Nov. 18. Sky partly covered with cirro-cumulus. Tempera- 
ture rising rapidly. Warm wave approaching. Wind W 
and WSW. 

Noy. 19. Sky clear, excepting a few cirro-cumulus. 
for the time of year. Wind S. 

Nov. 20. Weather cloudy. Sky nearly covered with alto- 
stratus and low strato-cumulus clouds. Cold wave during 
the night of the 20th and on the 21st. Wind SSW. 

Noy. 28. Sky partly covered with cirrus, cirro-cumulus, and 
cumulus. Flight made near the crest of a warm wave. 
It was difficult to begin the ascent on account of the light 
winds below, but as soon as the kites ascended a few 
hundred feet the wind was so strong that they were 
driven down and it was impossible to get higher. At the 
beginning of the ascent low fracto-stratus or scud clouds 
were drifting rapidly across the sky. The kites entered 
and temporarily disappeared in these clouds at an altitude 
of about 60 meters above the hill. The lower wind was 
light, and came alternately from the northwest and from 
the south, increasing in velocity to 4 or 5 meters a second 
when from the south, and diminishing to 2 or 38 when 
from the north. Above the hill during the entire morning 
preceding the ascent, the scud clouds were drifting rap- 
idly from the south. This southerly current descended 
below the level of the hill during the ascent, the scud 
clouds disappeared, and, later, cumulus began to form. 
Cold wave followed on the morning of the 24th. 

Noy. 25. Sky covered with strato-cumulus clouds, which 
grew gradually lower and light rain began at 12:35 p.m. 
The kites were brought down during a light drizzle. 
Wind ESE veering to KF. The kites veered 20° or more 
of azimuth to the right as they rose. 

Nov. 27. Storm passed off the New England coast during the 
night. Sky clear except for a few cirrus and fracto- 
cumulus. Temperature near normal, but decidedly lower 
than on the 26th. Wind NW. 

Nov. 28. Sky clear except for a few scattered cirrus. Wind W. 

Nov. 30. Sky partly covered by cirro-stratus and alto-cumu- 
lus, followed by clearing weather. About 11:38 a.m. the 
wind suddenly increased in velocity with the oncoming of 


Warm 


a cold wave, and the kites were driven to the ground 
without seriously injuring the instrument. ‘The record of 
the meteorograph and the behavior of the kites at the 
beginning of the ascent indicated that the wind velocity 
diminished with altitude. At this time the weather was 
partly cloudy and threatening, with dense sheets of high 
alto-stratus having cirriform edges. Later the sky began 
to clear, and the kite anemometer showed that the wind 
velocity increased very much aloft. ‘This increase aloft 
preceded a like increase below by about 40 minutes. 

Dec. 9. Sky covered with stratus, or low strato-cumulus, 
moving from the east. The kites left the ground in a 
northerly wind. At a height of about 270 meters they 
suddenly entered a strong easterly current above, and 
were soon partly obscured by the stratus cloud into 
which they entered. 

Dec. 10. Sky partly covered with a sheet of cirro-stratus. 
Cold wave on the 11th. Wind NNW. 

Dec. 12. Sky nearly covered with low strato-cumulus. Tem- 
perature very low. Wind N. Warmer on 13th. 

Dec. 21. Sky nearly covered with high strato-cumulus. Very 

warm for the time of year. Wind ESE. 

25. Sky covered with high strato-cumulus. Wind SE. 

26. Sky covered with low strato-cumulus and nimbus. 

Rain began at 4:15 p.m. Wind SSE. 


Dee. 
Dec. 


1896. 


Jan. 12. Sky nearly covered with a sheet of alto-stratus; 
cyclone centre approaching; minimum barometer with 
rain in the afternoon; wind south and increased rapidly 
with altitude. A warm wave with crest in afternoon. 

13. Sky partly covered with cirrus. Temperature fall- 
ing rapidly. Wind W veering to WNW, and its velocity 
decreasing from 9 to 7 meters per second. 

16. Sky clear except for a few cirro-cumulus. Kite 
meteorograph sent to an altitude of 1,824 meters, but no 
record obtained. 

17. Sky covered with cirro-stratus densest in the south- 
west. Storm central near Hatteras. Temperature reached 
a maximum in the afternoon. Wind NNE veering to NE. 
Kites shifted to the right as they ascended. 

18. The thermograph left the ground during a light 
snow. At 10:50 a.m. the thermograph entered the base 
of the nimbus. At 11:10 a.m. the thermograph and kites 
were drawn out of and below the cloud. On reaching the 
ground, the thermograph and kites, and about 100 feet of 
line, were found heavily coated with frost work. During 
the second flight, which was made in the afternoon, the 
snow had ceased, but the sky continued covered with low 
clouds. At4 p.m. the thermograph entered the base of the 
cloud and remained in the cloud until 4:16 Pp. om. 


perature fell during the day. 
27. 


Jan. 


Jan. 


Jan. 


Jan. 


Tem- 
Wind N veering to NNE. 
Steel wire first used for the kite line. Sky clear. 
Temperature considerably below normal, and reached a 
minimum at night. Wind NW. 

28. Weather clear; temperature decidedly below nor- 
mal: the minimum temperature of the cold wave occurred 
on the night of the flight. Wind NW. 

30. Sky partly covered with dense cirro-stratus, which 
entirely cleared away by evening. Temperature near 
normal. Wind WNW. 


Jan. 


» Jan. 


Jan. 


BLUE HILL METEOROLOGICAL OBSERVATIONS. 


Feb. 3. Sky covered with dense alto-stratus and low strato- 
cumulus or nimbus; light scattered flakes of snovy falling 
during the flight. Wind NE. 

Feb. 8. Sky clear during the flight except for a few scattered 
cirrus. A few fracto-cumulus observed in the early after- 
noon. Temperature above normal but falling. Wind W. 


Feb. 10. Sky clear except for a few strato-cumulus. Tem- 
perature near normal. Wind WNW. 

Feb. 12. Sky clear except for a few fracto-cumulus. Tem- 
perature below normal. Wind W. 

Feb. 15. Kites sent up during a southeast storm. Snow 


was falling shortly before the ascent, but this changed to 
sleet and rain about the time of the ascent and these 
continued to grow gradually heavier. The kites were 
driven down by the high wind above, and on reaching 
the ground were found to be coated with ice. The kites 
entered the base of the nimbus when about 30 meters 
of line was out, and soon became invisible. Wind SE; 
kites from SSE. : 

Feb. 17. Temperature extremely low. The lowest tempera- 
ture for ten years was recorded in the early morning. Sky 
clear except a few strato-cumulus on the east horizon. 
The first atmospheric electricity observed on the wire 
was noted to-day. At the highest point the potential was 
sufficient to cause the spark to pass through wooilen 
mittens. Wind NW backing to WNW. 

Feb. 18. The sky was covered with nimbus and light snow 
was falling during the flight. At 2:45 p.m. and with 
an altitude of 858 meters a fracto-nimbus obscured the 
kites and instrument for about half a minute. The sun 
was dimly visible from 2:47 to 2:55 p.m. Between 
2:55 and 3:04 p.m., at a height of 520 meters, fracto- 
nimbus were occasionally drifting under the kites, but 
the main cloud sheet was higher. Temperature decid- 
edly below normal, but rising. Wind NE veering to 
ENE. Kites shifted to the right, passing through an 
ENE into an E wind as they ascended. 

Feb. 19. Sky clear except for a few cirrus. Temperature 
below normal, but warmer than on the preceding and 
following days. Wind SE backing to ESE. 

Feb. 22. A new reel and register were finished yesterday, and 
to-day 1,600 meters of new music wire were wound on, in 
addition to the 640 meters previously obtained. Ascent 
begun at 4:37 p.M. Weather clear except for a few cirro- 
stratus. Temperature below normal but rising. Wind 
WSW veering to W. 

Feb. 23. Sky nearly covered with alto-stratus which rapidly 
increased in density, and light sprinkles of rain fell be- 
tween 4 and 4:18 p.m. Temperature above normal, due 
to the approach of a warm wave. In hauling in the kites, 
the pressure of the wire forced the drum-heads of the reel 
apart. Wind SSW. 

March 6. Sky covered with alto-stratus increasing in density, 
and followed by rain on the early morning of the 7th. 
Temperature near normal. At 6:04 p.m. the kites shifted 
suddenly from the southeasterly wind below into a south- 
erly wind above. A belt of light winds was found be- 
tween the two currents. Wind SE veering to SSE. 
Kites from § at the highest point. 


March 10. Sky covered with a sheet of cirro-stratus. Tem- 


perature near normal, 


EXPLORATION OF THE AIR BY MEANS OF 


March 11. At the beginning of the ascent the sky was coy- 
ered with nimbus, and a severe storm was approaching 
from the southwest. Snow began at 11:55a.m. At 11:56 
A.M. the kites entered a fracto-nimbus at an altitude of 
680 meters. At 0:25 p.m. the kites entered the main body 
of the nimbus at an altitude of 723 meters. At 0:02 P.M. 
electric sparks could be drawn from the line, and very soon 
they became so strong that it was necessary to ground 
the line. Began to haul the kites in at 1:06 p.m. By this 
time it was snowing hard. Strong electric shocks were 
felt whenever the ground wire was accidentally removed: 
The wind increased to more than fourteen meters per 
second, and the pull was so great that four men were 
nearly exhausted in winding the line in. When the wire 
was wound in to the upper 1,000 meters which had en- 
tered the cloud, the wire was found to be thickly coated 
with frost or fine snow, which fully doubled its diameter. 
At 2:20 p.m., while winding at the rate of about 0.4 
meter per second, the wind increased to about 16 meters 
per second (corrected to true velocity), and the wire 
parted near the instrument and the kites, all of which 
were carried away, but were afterwards recovered. Tem- 
perature near normal, but there was a cold wave on the 
12th. The clock cylinder was clogged and stopped by the 
snow about 0:40 p.m. The wind was from the E during 
the flight, and the kites continued to pull from the E at 
the highest point reached. 

April 5. The sky was nearly covered with strato-cumulus 
during the flight, but the sun shone on the instrument at 
intervals. Temperature below normal, but higher than 
on the preceding and following days. Wind NW. 

April 7. The sky was nearly covered with massive strato- 
cumulus, from which occasional light snow fell during 
the flight. At the end of the flight alto-cumulus were 


KITES. 


seen above. Temperature decidedly below normal. Wind 
NE. 

April 13. Sky clear during the first flight. Temperature 
above normal, and rising rapidly at the ground. Elec- 
tricity became strong when an altitude of 942 meters was 
reached, and was strongly felt at the highest point. In 
ascending the kites suddenly shifted from west-southwest 
to west wind, at an altitude of 524 meters, and in descend- 
ing suddenly shifted from west to west-southwest wind at 
an altitude of 470 metres. Wind WSW. 

April 18. Sky nearly covered with a sheet of cirro-stratus. 
Sea breeze set in while the kites were in the air, and the 
temperature fell rapidly at the ground. 

April 20, Sky partly covered with cirrus. Temperature de- 
cidedly above normal; a cool wave on the 21st. Wind W. 

May 20. Sky nearly covered with cirro-stratus. Wind SSW; 
kites from SSW at highest point. 

June 18. Sky clear except for a few cumulus. Temperature 
above normal and rising rapidly, due to the approach of a 
warm wave. Slight shocks of electricity were received 
from the line after the kites reached an altitude of 400 
meters. Wind S and SSW; kites from NW above 500 
meters. 

June 19. Sky clear except for a few scattered cumulus and 
cirro-stratus. ‘Temperature decidedly above normal and 
rising slowly. A cumulus passed the zenith between 3:22 
to 3:24 p.m., and drew the kites up to a steep angle. 
Wind W backing to WSW. 

June 20. Sky partly covered with cumulus and cumulo-nim- 
bus. Temperature continued decidedly above normal. 
Wind WSW. 

June 22. Sky about half covered with cirro-stratus. Tem- 
perature above normal but falling rapidly. Wind W 
veering to WNW and NW. 


Nore. — The direction of the wind is that of the surface wind on Blue Hill, and the altitudes are above the Valley 
Station, 180 meters below the summit of the Hill, unless otherwise stated. 


6 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


TABLE XVIIL. 


AIR TEMPERATURE AND RELATIVE HUMIDITY. 


Tate g great Air Temperature Humidity rae Dats = a! oO. Air Temperature Humidity 
and Fe | So won and Ey| Bob 
Hour, 28 Ses at on _in at on cals Hour. £5 Bq at on in at on 
sa) Ver | Kite. Hill. | Valley.) Kite. | Hill.| Fes 4A] 43> | Kite. Hill. | Valley.| Kite. | Hill. 
1896. 1896. 
April 8. meters, or: Baas ons p.ct. | p.ct. |m.p.s.§ April 23, meters. oF, OF, ake, p. ct. |p: ct. 
4:00 p |15| 355) 81.5 | 35.7) 38.9] 86 | 40 | 8.5 | 4:17 2 |} 3) 362) 56.8 | 62.0) 68.6] 32 | 26 
4:04e | 3| 445] 81.0 | 85.7] 88.6] 85 | 41 | 8.0 | 4:28e |] 8} 38711) 55.9 | 61.9) 63.5) 33 | 26 
4138p | 5| 578|°29.4)| 85.5) 88.4) 85°) 41/072 | yore 
4:25p | 5| 748] 27.2 | 85.2) 38.3] 36 | 42 | 7.6] 2:53e |] 8] 880} 44.1 | 49.4] 50.3] 40 | 34 
4:37 Pp | 5} 980) 24.3 | 35.0) 38.2) 34) 42 | 7.218:07 er | 6] 456) 42.0 | 49.1) 49.8) 40 | 34 
4:44p | 4) 887) 24.9 | 35.0] 37.8) 32 | 42 | 7.2] 8:23e 110) 608} 40.2 | 48.4] 50.0| 39 | 34 
5:03 ep | 6| 3884) 31.5 | 35.2) 37.8) 36 | 40 | 6.7 | 3:34e | 3] 608) 41.1 | 48.6] 50.8) 89 | 34 
recta 3:50 ep |10| 677] 41.8 | 48.5] 50.7] 39 | 34 
3:55 p |25| 296) 52.5 | 55.5] 58.6) 52 | 50 | 9.4] 38:58e ] 38] 755| 40.6 | 48.8) 50.6} 41 | 84 
4:13 ep | 5] 487] 52.6 | 55.5) 58.4] 5 50 | 8.5] 4:15 Pp 1/15] 802) 39.7 | 48.0} 50.6] 43 | 34 
4:25p | 7| 480) 51.0 | 55.2) O71) 57 | 51 | 7.6] 4:27 e | 8) 856) 38:4 | 47.2) 50:2) 44 | 34 
4:32 5 3| 540) 47.8 | 54.5] 57.0] 61 | 52 | 8.9] 4:35e |] 8] 887) 88.0 | 47.0} 49.8} 44 | 34 
4:49 p | 5] 603] 46.6 | 54.3) 56.8) 63 | 52) 8.0] 4:37P | 2) 892) 38.4 | 46.9) 49.8) 44 | 8 
5:03 ep |12) 814] 42.2 3.9] 56.3] 74] 52 | 85 74:42p | 4] 854] 38.6 | 46.8] 49.8) 44 | 34 
5:20 ep | 5| 673] 48.2 | 52.7] 55.5) 74 | 53 | 8.5] 4:55e | 5) 648} 40.4 | 46.38) 49.8) 42 | 38 
5:30p | 2| 564] 44.6 | 52.5) 55.4) 71 | 58 | 7.2] 5:05e | 38] 501] 40.4 | 46.2} 49.1} 39 | 40 
5:34e | 4) 483) 46.8 | 52.5) 55.8) 68 | 538 | 6.7 | 5:16P)] 38} 346) 42.0 | 45.9) 48.6) 42 | 43 
D425 psa ol 2a) ae 52.4| 55.0] 66 | 54] 6.7 | 5:26e | 4} 210] 43.8 | 45.5) 48.3} 44 | 44 
April 13. April 27. 
3:37 e | 4| 829) 77.0 | 81.2] 88. 39 | 3 7.21 5:18pP | 3] 203) 49.7 | 49.5] 51.7} 62 | 59 
3:54 Pp | 6) 028 |) F434) 82 8377 | 42585 1 1.6: 5:27 Same Oe Sete oe elon ora! (60 
4°16 © | 12)) 6959 T1e7 a) 2S0:2)/8 3126) F450 ST eS-0) 15:40 Paleo Maem ScOn melon mm Oye | 62 
4:25p | 4| 742] 69.4 | 79.5) 81.5) 45 | 8 7.6 | 5.50P | 4] 266] 47.7 | 47.6] 51.3] 68 | 64 
4:43 pe | 5] 899] 67.4 | 79.3) 81.8) 47 | 87 | 63 16:04e | 5] 804) 48.2 | 46.5) 50.5] 63 | 66 
5:23 p | 4/1060) 65.4 | 77.8| 77.4] 45 | 40 | 7.2] 6:06r | 2] 346] 48.2 | 46.4] 50.3} 64 | 66 
5:28 Pp | 4) 1221) 644°) 77.6) 76.8) 46 | 42) 6.7 1 G12P | o 4)) Qi2 4615 46 e497) 67 | 68 
5:32 Pe | 3/1370) 62.0 | 77.1} 76.5) 45 | 42 | 7.6] 6:14e |. .| 266) 45.5 | 46.1] 49.2) 68 | 69 
5:88 ep | 4/1336) 62.6 | 75.9) 75.1] 44 | 42 | 6.7] 6:20e | 38) 200] 45.5 | 45.5) 48.9} 71 | 71 
6:02 p | 6/1089] 66.9 | 73.3} 72.6] 42 | 46 |°4.9] saya. 
6:20P | 6] 891] 68.5 | 72.8) 70.5] 438 | 48 | 5.8 | 2:00P |]. .| 281] 72.8 | 74.0| 76.1} 46 | 42 
6:35 Pp | 2] 620] 72.5 | 71.6} 68.7) 438 | 48 |) 5.4 | 2:18P | 1] 583) 67.0 | 74.7) 76.8) 50 
6:50 Pr | 7| 401) 72:1 | 71.2) 67.6) 43 | 49.) 6.3 | 2:25e ) 4) 455) 68:8 | 7405) 76:2) 51 
1:02P'| 5) 227 )-70.8..| 70.37 67,0.) 49 1°50.) 6.3.) 2:40 © GIG Ga7 ar (3.0 70:8) 55 
fener | 3:20p | 6| 480] 69.7 | 74.5] 78.0) 45 
4:54p | 6] 208) 76.2 | 76.9] 78.2) 387 | 37 | 6.3.1 3:55P | 3) 533) 69.2 | 76.2) 78.2) 45 
5.06P | 6| 277| 76.6 | 76.1) 77.0} 39) 38 | 6.3 | 4:36P |- 6) 780) 64.7 | 76.6) 78.5) 48 
5:04 pel 4294) 762 Ae 0.0) 3 ale 4 | A507 enon Aue Oe mma OhealeriSeon lame) | ae 
5:49 ep |10| 384) 78.7 | 72.5) 72.8) 41 | 46 | 5.8 |] 5:12P | 4)1208) 57.5 | 75.8) 77.9] 55 | 41 
5:54e | 5| 452] 73.9 | 72.3] 72.61 41 | 46] 5.8] warz 
1 6:05 e 483| 73.5 | 72.0] 72.4] 41 | 47] 5.8] 2:53 | 5| 383] 87.7 | 44.8] 48.6] 61 | 54 
16:09r | 8} 583) 69.4 | 71.8] 72.3] 43 | 47 | 6.3] 3:04P | 7] 558] 35.7 | 44.6] 48.1] 46 | 55 


EXPLORATION OF THE AIR BY 


Wate eS a13. Air Temperature Humidity 
and Egat Bot 
Hour. |28/)3653 at on in at on 
sa| sar | Kite. Hill. | Valley.| Kite. | Hill. 
1896. 
May 7. meters.| °F. oF. OF. | pict. |p. et. 
| 3:15 p | 5]. 755]|.35.2 | 44.3) 47.4] 386 | 56 
3:24p |} 3] 797] 33.9 | 43.9} 46.9] 384 | 56 
3:42 p 110] 781] 84.8 | 43.8} 46.3] 31 | 58 
3:49 p | 81.1075) 35.2 | 43.6] 46.38} 29 | 59 
3:54p | 3] 981] 35.0 | 43.5] 46.3} 29 | 59 
4:15 p |13/1026] 36.6 | 48.3) 46.3} 25 | 60 
4:31 Pe |} 8] 992) 35.9 | 48.3) 46.2} 25 | 63 
4:39 p | 3} 988] 35.7 3.2) 46.3} 27 | 62 
4:45 p | 4) 901] 35.5 | 43.2] 46.5) 28 | 62 
4:57P | 7] 814] 86.9 | 42.9) 46.8) 32 | 61 
5:08 ep }75|, 736) 37.8 | 42.9) 46.5) 33 | 61 
5:17 p | 4] 568] 39.5 | 42.9] 46.1] 382 | 61 
5:29 ep | 4] 3938] 39.0 | 42.8) 46.2] 48 | 60 
May 8. 
3:03 vp fea) 831) 61.6 | 67.7} 69.2) 42 | 41 
3:13 P| 3] 472| 59.38 | 66.3) 69.0| 44 | 41 
4:20 p | 6] 866 
May 9. 
2:05 p Ha er2s0)|) 74.5 | 76.41 81.71°.55 | 59 
2:10 p (ay 9827) 71.9 | 76.1) 81.6) 58 |.59 
2:20e } 4| 428] 71.2 | 75.5] 80.4) 60 | 60 
2:35 P lo 482)/° 72.5 4) 74.7 | 79.4), 62 1 60 
2:36.P\ We o24 | 72.30) T4.7 |) 794 | 62) 60 
2:37 Pe OFS). ome Sli acaear) Oe 
2:43 P| 3| 754) 69.6 | 74.4] 78.4] 64 | 60 
2:51 PMS Oe O76 4) 73.8) 77.0) Oo i GI 
3:04 Poneu0se || 07-8 14.78.01) (77-2) 68 ih 59 
3:12 Pp | 2/1145) 68.7 | 74.8] 77.8) 53 |-59 
3:38 P | 19| 1332) 69.6 | 71.9] 76.1} 40 | 61 
3:58 P Wet 126) 71.24). 71.8) 75.5.) 43) | 61 
4:15 Pp } 4) 962) 72.7 | .70.0| 75.2| 51 | 62 
4:32 Pp 13) 782) 74.8 | 71.1) 75.2) 53 | 62 
4:43 Pp | 3] 3138] 78.1 | 70.0) 73.6] 56 | 63 
4:49 Pp | Ly 250) 70.3 | 70.8) 73.1] 62 | 63 
May 14. 
4:35 Pe | 4] 3888] 65.8 | 69.6] 71.8] 62 | 61 
4:58 p |20| 559) 63.7 | 69.38] 71.3) 66 | 64 
5.14e |10| 553| 63.7 | 67.9] 70.8| 67 | 70 
| 5:27r | 4| 883) 62.0 | 66.5] 69.8] 87 | 73 
June 2. 
4:00 e | 6| 360} 60.1 | 64.1} 67.8) 51 | 49 
4:20 p |13} 560! 57.8 | 64.3! 68.31 53 | 50 
4:30 P | 8] 608] 55.5 | 64.2} 68.8] 55 | 48 
4:48P] 8] 872] 51.8 | 65.3) 67.8] 58 | 49 
4:58 pep } 4] 892] 51.3 | 64.8] 67.7] 59 | 49 
5:27 ep | 6| 1084) 48.1 | 64.0} 68.0} 63 | 49 


MEANS OF KITES. 


77 


Date . gi | ak Air Temperature Humidity (ye 
and iy) AE tices | ete 
Hour, [28/23¢| at | on | in | st | on | eae 
Aa) tae Kite. Hill. | Valley. | Kite. | Hill. | Pes 
1896. 
June 2, meters.| °F. PUT oF. | p.ct. | p. ct. |m.p. 8. 
§.55p}15| 878) 50.4 | 63.3) 67.2] 61 | 51 | 9.4 
6:12e] 3] 665} 53.8 | 62.7] 66.4] 57 | 51 | 8.9 
6:23 p| 3] 480] 56.8 | 62,2] 65.8] 56 | 52] 7.6 
6:41P] 2] 206} 60.6 | 60.8] 64.3) 55 | 54 | 7.6 
June 6. 
10:054|}10} 446] 52.9 | 60.3] 61.4] 88 | 79 | 10.3 
10:20 4/12) 560] 57.4 | 60.0} 61.2) 60 | 76] 9.4 
10:35 4} 9] 640) 57.4 | 60.8] 61.5) 61 | 77 | 7.2 
10:454| 3] 842] 57.9 | 60.4] 61.7| 62 | 77 | 7.6 
0:12 P| 43] 700) 56.0 | 60.7| 62.0| 707 79 | 8.0 
0:18 P| 6| 769) 55.6 | 60.8] 61.8) 70 | 79 | 6.7 
0:35e/11] 776] 56.9 | 60.4) 62.0) 69 | 78 | 6.7 
0:40 2] 4] 726) 57.0 | 60.4] 62.2) 69 | 78 | 8.5 
1:04 P| 8]' 806] 56.5 | 61.3] 68.2) 70 | 71 | 6.7 
1:56e| 4/1018) 55.1 | 59.9) 60.1) 70 | 84) 8.5 
2:49 P| 6} 981] 55.6 | 57.8] 59.5] 76 | 86} 89 
3:lle| 7} 874] 56.9 | 57.7] 59.2] 74 | 86] 8.5 
4:00 ep}. .| 1006) 55.6 | 56.1] 57.5) 75 | 94) 6.7 
4:42 Pp}. .| 470| 58.2 | 56.9] 57.8] 88 | 90] 5.4 
4:46P]..| 470] 54.7 | 56.1} 57.8] 83 | 90 | 4.9 
4:48 P|. 441) 55.4 | 67.2) 57.8] 86 | 91 | 4.9 
4:49 P|. .| 406| 54.0 | 57.2) 57.8) 89 | 91) 49 ] 
4:538p]..| 402| 52.9 | 57.3] 58.0) 91 | 91 | 49 
4:55 P|. .| 862) 53.6 | 57.1} 58.0| 92 | 92 | 4.9 
4:56 PR}. 296| 54.5 | 57.1) 58.0} 92 | 92 | 4.9 
June 11. 
4:56pe| 5] 190} 64.0 | 66.6] 69.5] 48 | 50} 8.0 
5:07e| 8| 270] 63.8 | 66.6] 68.9) 46 | 48 | 85 
5:21P] 5| 5384] 59.1 | 65.9| 68.9] 45 | 46 | 12.1 
5:30e| 4] 631] 57.6 | 65.7|.68.4] 46 | 45 | 11.6 
585 pi 2) 780) 66.3 |.65.6) 68.1) 47 | 45 /121 
5:38 pe] 8) 747| 55.6 | 65.5; 67.8) 46 | 45] 9.4 
6:19Pe| 8] 273] 68.1 | 64.4) 67.6) 44 | 48 | 8.9 
June 12, 
5:08p| 3] 831] 60.7 | 63.3) 68.0) 53 | 53 | 5.4 
S:llp| 2] 268] 61.6 | 63.3} 68.0 53 | 4.9 
June 13, 
5:18 Pe} 2] 320} 57.8 | 58.5) 62.0] 68 | 60 | 63 
5:45p|] 4] 866} 58.8 | 57.9] 61.0} 75 | 61] 63 
§:51P] 6] 456] 58.8 | 57.8} 60.5] 76 | 61 | 5.4 
5:58 Pe]. .| 441] 58.4 | 57.8] 60.4) 76 | 61 | 5.4 
6:00r| 8! 4431 57.1 | 57.7! 59.9} 83 | 61 | 6.3 
6:12P| 3| 356} 56.1 | 57.4| 59.5| 80 | 62) 63 
6:22P| 4| 212] 56.1 | 56.9| 59.3 6.7 
June 17. 
2:32P| 4| 496| 62.1 | 67.6] 72.9 57 | 10.3 


78 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


Air Temperature Humidity Air Temperature Humidity 


Date 
anil 
Hour. 


Date 
and 
Hour. 


at at on 


Interval in 
Minutes. 
Altitude 
above 
Velocity 
on Hill. 
Tnterval in 
Minutes. 
Altitude 
above 
Valley. 
Velocity 


at on in at on 
Kite. Hill. | Valley.| Kite. | Hill. 


| Valley. 
Wind 


on i 
Kite. Hill. -| Kite. | Hill. 


| 


1896. 1896. 
June 29, eters.| OF. : . | pict. | p.ct.|m.p.s.J July 22. Fergal ques SAVY OMe Dp. ct. | pacts 


2:29 e 3 ale One 10: 9. 50 9 CUAG Bio ones fi. | oe 
DO Ee 304 | 68.4 6 fre} || tail : : OSU OOAMOeo |, . | C0 
2:48 Pp DG523 Da : 57 : a2 COBRA 83.2 ite 
3:03 P| 6 § 60.8 (0 ; 63 | ¢ ; : 65.5 | 76.2) 82.0; .. | 80 
3:18 P 2! 57.9 : B.3/ 70 SH) ID ||. 65.8 | 74.9] 80.8) .. | 88 
8:21 P83 | 12383 ) OS 5 | 70 : Sad 6G.L ee 7oI0N 80:8)... | 82 
3:56.P)) ee alias 56.8 ip. 9. (Bi ike ; :2 64.0 | 78.2) 80.5) .. | 85 
4:00 Pp 60 | 74.8 3.0 : 48 S 46 é 64.6 Tooneee. || Oo 
July : 67.5 79.8| .. | 86 

3: 56.5 | 59. 2: Af ; : 67.6 TOO. . |-89 
54.7, 9. 32. ihe 8 : ; es 68.2 78.6 
68.7 2.9} 77.8 


July 10. 
2:44 P Sie Je . O41. : A ‘ 5 74.0 ov 79.8 
2:56 P y é .6| 87. : é : 71.3 .2| 79.6 
Oo 20 sPie eel one os S4. 86. we SA: 70.0 is 80.0 
3:31 P| 5] 8 “e : ely 4: ; : f 65.5 11 80.0 
S42 P38 : i ) 3 Be 64:3 :aliee een O so 
SPO TEP Mies bul. F2e : s 8. 2:48 sg GO 4 aie eo: 
1 1\0 Re eament tate) S 6 3.8| 86.3 | ile 3:36. Py 8 478), 69.2 2 
4-93 p 37 P 3.2 5.8 ) ). Bye) 122 |) 34] 68.6 
July 20. Brat 1 Ih. 35 | 60.6 
9:30 4 | , 2. 2 : : 8:56 P (ial 
9:40 A 4:13 P 58.6 
10:38 A 4:25 Pp 55.8 
10:47 A 4:37 P 53.2 
10:54 a 4:44 p 51.4 
11:044 4:59 Pp 50.9 
11:14 a 1700 5:31 P 53.7 
11:29 a 1795 6:08 P 62.7 
0:19 p 1950 6:15 Pe 67.7 
1:10 P| 3/1290 Auge 
1:26 P | 1095 2:51 P 
| 1:34e|. .| 1131 3:05 P 
2:09 P 8357 3:23'P 
2:23 ep} 4]. 666 3:59 P 
2:38 P 484 4:12 p 
2:51 P 854 4:18 Pp 
July 22. 4:25 P 
IIS PAN 380 4:29 p 
0:02 Pp 544 4:34 p 
0:16 P 716 4:49 p 
1 0:28 Pp 880 4:46 P 48.0 
0:42 Pp al 4:52 Pp 49.6 
0:56 P| 3|1418 A:54 Pa 49.5 
1135p 1540 4-5 Sip leet Oa Ou 


or 
Se 


em ee Oro 
oc © =I 


-~I 
ies) 
cr Oo b ¢ 


=I 


“1 
~I 0 00 ~ 


wWwSoeSooeowHwwt 
or 


“I 


So 


| 
Oo co EH bd 
a 43 
-~TI +I +] 
oo 0 bS 
ry Pes fas | 
“1-10 © 
> oH 
BD 


=] 


oo 0 0 Ht © 
oO 
~I 

WD 

5 


C= 5 


~!I 


bp ow oP bo 


= 1 


~1 
to te (She) 
-~I -I] 
~I a © 
~I -1 -] 
[or] 
or or & 
~I +1 
s= he Se 
b co 


aT -J 1 s+] <1 
He ow 

Sv Go Oy ea 

~“I -1 -+J <=] 
S10 ID SID IC 

BPreonw oO FR Fe DOF OC 
-~I 
> or OD 


aI -I 
=~] 
“1 0 


46.9 
45.0 
46.2 
48.4 
49.3 
48.6 
48.2 


oe ee 
“I 


co 
[ome oS) 
(9 ) 
1 =] 
or oo 


=~I 


CO 


oO oO Co 
me OOo © RK bb bo 


wwe oarw —& ROO ee Lb 


=~I =I] 


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aoe 


EXPLORATION OF THE AIR BY 


Date 5 alg. Air Temperature Humidity b>. 
” 183 | e235 Kite. | Hill Watley. Kite. | ai. | EE 8 
1896. 
Aug. 1, meters.| °F. a oF. | p.ct. | p. ct. |m. p. 8. 
5:20 P|} 3/1596] 46.2 | 67.6] 73.6] 40 | 58 | 8.0 
5:38 P| 3/1290} 50.4 |} 69.3) 72.2) 75 | 48 | 9.8 
5:53 P|} 3/1198} 52.7 | 68.9} 71.0 47 | 8.5 
6:09 P| B)/) 849] 57.2 | 68.1) 69.2 48 | 8.5 
6:28 pe) 8) 518} 62.1 | 66.7| 67.2 48 | 9.4 
Aug. 17. 
10:41 a eee 1 69:6 173.2) 75.8 - 71 | 61} 7.2 
11:004| 1}| 556] 66.0 | 73.1] 75.4) 78 | 66 | 5.8 
11:50 a) 1) 902) 60.7 | 73.9) 77.2 57 | 8.5 
11:55a] 1} 767) 63.5 | 73.9) 76.7 57 | 7.6 
0:06 Poe 940866153) 74.1 | 77.2 54 | 7.2 
0:23 Pies 2On TOLL Wef4. 3 eivel By | 10” 
0:57 P| 1] 980} 59.9 | 74.0 . 48 | 7.2 
1325 Pp MSF 426) 70.7 | 75.1) 76.5 45 | 6.7 
23 Pie G26) 07.8) (OL io.d 44 | 6.3 
1:30P | 1] 604) 68.0 | 73.9} 75.2 45 | 5.8 
Aug. 22. 
2:08P|14| 461) 64.3 | 68.7| 72.6) 82 | 71 | 8.0 
2:23P| 6| 666) 60.1 | 69.0| 72.5) 94 | 71 | 8.0 
2:38 Pe] 4] 880] 57.3 | 68.9] 72.4/100 | 70 | 7.2 
2:58pP| 6| 933] 56.0 | 68.8] 72.4|100 | 70 | 5.4 
3:28 P| 4/1014) 55.2 | 67.7] 70.6) 99 | 68 | 8.5 
3:43 p| 3/1156 | -52.9 | 67.8] 70.5] 100 | 69 | 5.8 
4:10 P| 4]1232] 52.1 | 68.8] 70.8| 100 | 69 | 6.3 
4:12 p 1265} 51.9 | 66.9] 70.8] 100 | 69 | 5.4 
4:27 P| Saf 1176) 52.2 |.66.9} 71.2) 100 | 71 | 5.4 
4:41 p| 7/1259] 51.6 | 68.7) 70.8] 93 | 70 | 6.3 
4:50 P Beepls18 | 51.8 | 67.6) 71.4) 87 |. 71) 7.2 
5:12 P| 3/1168) 54.8 | 66.6] 70.3} 89 | 74 | 8.0 
5:31 P]. .|1008|] 55.3 | 65.9} 70.0] 77 | 77 | 6.7 
5:48 P|} 4] 752] 59.5 | 65.8 69.1) 75 | 80 | 8.0 
6:02 P 472 90° | .81 5 FeG 
Aug, 26. 
4:13 Pieogeouly 67.9 | 73.2 |,78.0| 52 | 46°) 7.6 
4:28P | 5) 800} 62.8 | 72.6) 77.7) 60 | 45 | 8.5 
4:48 p| 4/1041] 58.0 | 72.0] 77.2| 74 | 48 | 6.3 
5:15 Paolo o0.04 170.4) 75.61" 82.1 5h.) 6.3 
5:27 P| 711403] 52.6 | 70.0) 74.0| 62 | 52 | 5.8 
5:46 P| 8/1562} 49.9 | 68.1| 71.0} 59 | 63 | 5.8 
6:01 Pe}. .|1693] 48.1 | 66.8) 68.9} 59 | 67 | 6.7 
6:22 P|} 3/1667} 48.2 | 65.9| 67.2| 59 | 70 | 7.6 
6:29 P 1692.) 48.1 | 65.6| 66.9] 57 | 70 | 7.2 
6:42 P 1667 | 48.2 | 64.9} 66.0} 54 | 70 | 7.2 
7:00 P 1665] 48.1 | 63.8| 65.4] 46 | 73 |.8.5 
8:10 P|. .{ 1525) 51.9 | 62.0) 64.2) 46 | 73 | 8.5 
8:58 r| 7/1828} 55.3 | 61.2} 61.6) 43 | 77 | 8.0 


MEANS OF KITES. 


~I 
io) 


Date 5 ace Air Temperature Humidity bm. 
Mom VEE | S22 | xlte, | Hit |-velley.| wite, |n, | BS = 
1896. 

Aug. 26, meters,| °F. OF, OF, | p.ct. |p. ct. |m.s.p 
Spiess | yl ae Pal) conc) || Conley Xeteesy.|) ey Ay vide 
928'P] 6 | 925) 56.9 | 60.9} 59.8} 70 | 81 | 6.7 
9:42P/} 6 | 560| 60.8 | 60.1] 58.2) 86 | 86 | 6.7 

Aug. 31. 

10:16a| 3 | 496} 62.6 | 72.2] 75.4| 78 | 60 | 8.5 

10:344; 8 | 915} 57.6 | 74.2] 76.2) 84 | 58 | 6.7 

10:41 a} 3 | 1183 TAA TEE ce 1 8S-1.8:0 

10:54 a]. .| 1273 75.1] 76.9|100 | 57 | 7.6 

PU:00'Ae 2b 1410} 2). afc Tell ks PN AAU ee sade 

11:124]. .| 1542] 55.4 | 75.9] 77.4] 54 | 56 | 6.7 

11:23] 2 |1470| 55.6 | 76.5] 77.4] 53 | 56 | 7.6 

11:344 | 4 |1771| 51.5 | 76.0] 77.9 55 | 8.5 

11:38 4 | 4 |1816| 50.2 | 77.3} 78.0 55 | 7.6 

11:59} 5 | 2123| 46.8 | 75.6] 76.2| 70 | 56 | 8.6 
Sept. 8. 
4:12P], .| 280] 58.4 | 58.7| 62.2} 55 | 65 | 8.0 
4:34e| 4 | 470] 55.6 | 58.1] 61.4] 55 | 69 | 6.7 
4:47P| 3 | 801] 57.0 | 57.9} 60.8] 38 69 | 7.2 
5:05e| 9 | 1244} 55.9 | 57.3} 60.3] 28 | 74 | 6.3 
5:26e | 3 | 1372) 50.4 | 56.9) 59.3) 29 | 78 | 7.2 
5:29e|]. .|1860| 55.4 | 56.7} 59.3} 29 | 79 | 6.7 
5:42 p| 3 |1255| 56.4 | 56.4] 58.8} 29 | 82 il 
§:54P| 4 11098] 57.7 | 56.1) 58.3]. 27 | 84 | 7.2 
6:07 e| 8 | 790] 55.6 | 56.0] 58.3] 42 | 83 | 7.6 
6:22 Pr 1-2 | 482) 97.2 | 56.1) 57.6)--53 | 83 | 7.6 

Sept. 11. 
4:54P| 3 | 475| 77.4 | 79.1} 82.9) 70 | 75 | 5.4 
D0SPhs | 612) 79.9 1°78 SL) Tbh 16-1 5.4 
5:15e| 3 | 617} 75.9) 77.7) 80.8} 71 | 76 | 5.8 
5:31e| 4} 471| 77.4 | 76.1] 78.8} 70 | 78 | 63 

Sept. 16. 
9:464| 4 | 488] 53.1 | 59.9) 63.8; 99 | 75 | 7.6 

10:024| 3 | 590] 51.4 | 59.3} 63.7} 100 | 75 | 8.0 

10:28 a} 4 | 511) 51.0 | 59.1] 63.7}100 | 76 | 7.2 

11:00.4| 5 | 576] 52.0 | 60.3] 64.3)100 | 76 | 7.2 

11:19 a] 4 | 601) 51.7 | 60.0} 64.1} 99 | 75 | 7.6 

11:364| 2 | 890] 54.2 | 60.0} 64.5] 85 |,75 | 7.6 

11:504] 7 | 894] 54.9 | 59.1| 64.4) 87 | 77 | 6.7 

11:55.a| 4) $92) 54.2 | 59.1) 644) 901) 77 | 6.3 
1:01 P|] 4 | 522) 55.3 | 59.1} 64.9) 73 | 80 | 6.3 
1:23 e| 3'| 478] 58.4 | 58.9] 68.4] 98 | 81 | 7.2 
1338 Prd. 1281) 55.7 | 59.38 1°63.2 | 90.) Sl | 6.7 
4:07 P| 4 | 516] 56.2 | 56.5] 59.7 88 | 7.2 
4:09r| 2 | 520| 56.1 | 56.2] 59.8) 70 | 88 

Sept. 17. 

2:32 P| 4 | 478) 59.0 | 64.4] 69.3] 85 | 78 | 8.0 
2:36 P| 3 | 399| 59.7 | 64.3} 69.2] 83 | 78 | 7.2 


80 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


Air Temperature Humidity Air ‘Temperature Humidity 


Date 
and 
Hour. 


Date 
and 
Hour, 


at on at on 


at on at on | in ) 
Kive. Hill. | Valiey.| Kite. | Hill. 


in 
Kite. Hill. | Valley.| Kite. | Hill. 


Interval in 
| Minutes. 
Altitude 
Interval in 
Minutes. 


above 
Velocity 


Valley. 
on Hill. 
Altitude 
above 
Valley. 


Wind 


| 


1896. 1896. 
Sept. 17. meters, or: oF. oF. | p.ct. | p.ct.|m p.s.| Sept. 29. meters. on, oF, OF: | p. ct. |p. ct 


2:55 Pp 839] 53.5 | 68.4] 68.0] 100.| 84} 6.3] 4:37P]..| 7 50.4 | 58.6} 60.9| 91 | 86 
3:08 p 1036] 55.0 | 63.8] 68.0} 80] 85 | 7.6] 4:43P]..| 917] 58.7 | 58.3] 60.8] 100 | 86 
4:17 P 57.8 | 63.2| 66.4] ..| 84] 7.6] 4:49P| 4 11054] 52.6 | 58.0] 60.8] 100 | 86 
420 P| 8] 507] 57.3 | 68.8] 66.4| .. | 84] 8.5] 5:06P], .| 1334] 50.8 | 57.2] 60.0] 100 | 87 
Sept. 18. 5:18 P 1450} 49.0 | 56.7] 59.8|100 | 88 
10:03 4 33| 57.1 | 62.8] 6 53 |12.1 | 5:22]. .|1460] 48.5 | 56.7] 59.8) 100 | 89 
10:184| 3] 652] 54.6 | 63.1 53 3] 5:36e]. .|1586| 46.5 | 56.6] 59.2] 99 | 90 
10:324].. 52.7 | 64.0 SAP Ort || Bae 
10:48 4]. .| 1024] 49.8 | 65.2] 67. 52 | 8.5 11:08 4 278| 44.0 | 45.5] 49.4 
11:07 4] 5| 890] 53.2 | 65.9] 68.! 50 11:21 4 502} 41.4 | 46.0] 49.5 
11:20a| § 54.0 | 66.0! 69. 51 .6111:294] 4 | 630] 39.7 | 46.1] 49.5 
11:32 4 301] 57.8 | 66.3] 69. 50 | 8.9 ]11:454]..] 499] 39.6 | 45.3] 48.4 
Pii:tta 5| 61.2 | 66.2| 69. 9 | 48 | 10.8 ]11:54.4]. .| 498] 40.0 | 44.9] 48.4 
| sept. 19 0:15 P 798 45.1| 48.7 
3:49 P| 4 2| 67.8 41 77.8) 98187 0:17 P| 2 | 776] 36.7 | 45.1] 48.7 
3:53 P 66.9 DE ie ar 90 0:28p]..| 860] 36.2 | 45.8] 49.8 
4:00P].. 69.9 . : 89 0:42p|..) 577 6 | 46.1] 49.8 
Sept. 20 0:45 p 498 | 41.7 | 46.1} 49.8 
3:39 P : ‘ sy 4.9 ah d Sead Oct. 8. 
3:46 P| 5 9. Bd em. |e: . . | 10164 611 8 | 47.9] 48.9 
5:44 pe] § EEO ings: 3 Shoe as bee . . 110:48.4 798| 36.6 | 46.7] 48.9 
10:05 p 5 My J per . . (11:00 P4826 DA 7a t9. 1 
Sept. 24 11:05 a 938 47.6] 49.1 
2:12 Pp 395 6 | 58.6] 68.8] | 4111204 776 47.1] 49.2 
2:14 P 3 3.8 | 59.6) 63.5 f 4 Y11:394 528 46.9 | 50.0 
2:19 Pp : 4 | 60.5] 68. E : 0:31 Pp 5d1 A ieeoO.2 
241 Pp] 3} 38¢ 9 | 58.5) 62. 3] 0:55P 957 47.9| 50.4 
3:33 P 365 | 55.3 | 56.7] 60. ; 8 | 0:59P] 2 | 1098 47.9| 51.3 
4:01 P : if 57.8 .c Qt USP Se o0s A8.3| 51.4 
Sept, 25. 1:35 P 1370 6 | 49.4| 52.3 
3:01 p|..| 587] 53.7 | 61.2| 67. ; 9.4] 1:45P 1355 | 29.4 | 48.8] 52.6 
3:26 P| 20) & 52.9 | 61.4] 66. 5 | 1:47P]. .|1396| 28.7 | 48.8) 52.5 
3:38 P|12| 52: 4 | 61.0] 66. ) | 6 3] 1:58P]. .|1858| 28.3 | 49.0} 51.6 
8:50P]..] § A | 59.9| 65. | 941 2:20P] 5 11599} 25.5 | 48.7] 51.9 
3:55 P| é .2 | 59.8] 65. 3 Al 2:59p 1446| 27.2 | 48.0} 51.4 
08e|..| 526] 538.6 | 59.0] 64. 0.8] 3:28P). .|1920| 27.1 | 47.8} 50.3 
5:3! 54.3| 57.2 5 A] 3:34 P!.. .|1588} 25.1 '47.41 50.2 


on 
(o2) 


boa 


to 


BRIS chal oes: [BS 
Roc 6S BS: 


co wm C2 co 
SYP AE 
IEE eS 


~1 bo 


iS 


~ 


oo 


oo 


Pave D2: ). 54.0 ay j 9} 4:20 P 2470) 28. 46.6 | 49.8 


5:56 ¥ 53.4 55.! 9] 4:41P|. .|2828| 20.4 | 45.8] 48.7 
Ba 5:12 P|. .|2489) 23.6 | 45.3] 47.8 
3:27 P|. .| 286] 59.8 | 61.6] 64.1| 73 | 7 71 5:48pe]. ./1940| 27.9 | 44.6] 46.6 
3:35 p| 2| 323] 58.9 | 61.3 6:18P|. .|1625) 23.6 | 43.6] 44.8 
3:44p| 3] 303 0 | 60.6 6:36P|. .| 1495) 25.0 | 43.5) 43.6 
8:54p|..| 4551 55.7 | 60.4 7:17 P|...|1405| 26.3 | 42.3] 40.0 
4:12p| 3| 685] 51.5 | 59.5 7:35P|. .|1425| 26.3 | 41.6| 38.4| 
4:97 P| 8 0 | 58.7 8:10P|. .|1395| 26.3 | 41.1] 87.1 


© 
~ 


“Io t 


a 


EXPLORATION OF THE AIR BY MEANS OF KITES. 81 


Air Temperature Humidity Mate Air Temperature Humidity 


and 
Hour. 


at on in on at on in at on : 
Kite Hill. | Valley.| Kite. | Hill. | 


at 
Kite. Hill. | Valley.) Kite. | Hill. 


Interval in 
Minutes. 
Altitude 
Interval in 
Minutes. 
Altitude 
above 
Valley. 
Velocity 
on Hill 


above 
Valley. 
Velocity 
on Hill 


| 


1896. 
Lal oF, oF, p. et. . ct, .p.s.] Dec. 12. oR: oF. oR. p. ct. |p. ct, 


30.3 | 41.3} 87.0] 70 3.7 7 10:15 a 31.7 | 36.9) 39.1] 87 | 76 
37.2 | 40.5/ 85.9] 62 7 110:40 4 36.7 | 37.4| 40.4] 83 | 76 
41.7 | 39.9] 35.3] 58 ; 2:15 P 40.3 | 44.2} 46.4 63 
2:28 P 38.5 | 44.2 | 45.7 63 
66.9 | 72.1] 73.9} 47 : 2:33 P 36.7 | 44.8) 45.7 63 
65.6 | 72.0] 74.0} 49 : 2:45 Pp 42.38 | 44.4] 45.7 
66.1 | 69.0) 71.4} 49 | « 2:50P) ¢ 40.3 | 44.5} 45.6 
62.5 | 68.3] 70.5] 57 ; 207. P Le 87.8 | 44.5) 45.6 
60.2 | 67.7) 69.7] 59 , 3:03 Pil, 44.8 | 44.5] 45.8 
55.7 | 66.7} 68.3) 65 : Do OcPalnare 10 | 37.2 | 44.5) 44.9 
d+.6 67.9| 65 F 3:22P|.. 39.8 | 44.4] 44.3 
Dec. 15. 
66.7 8.2) 71.3 : 2:10 22.7 | 26.6] 30.0 
63.2 .9| 70.8 : 2:19 P 18.8 | 26.5} 29.9 
58.0 9} 70.5 2:27 P 15.5 | 26.5} 29.9 
53.3 7.6) 70.4 2:36 Ph5 « 16.5 | 26.6} 29.8 
49.2 1.4| 70.0 ; 2:42P].. 18.4 | 26.4] 29.5 
2:55 P 22.9 | 26.2) 29.4 


— 
_— 
(Se 
Oo 
_ 
o 


43.8 1} 69.5 


1897. 
Heal oT anes Jan, 2. 
51.0 ae Gis) are : 0:01 P 
51.7 Deo OO: OH arene ; 0:07 P|. 
61.3 sHtOOnLe meres ) : 0:14 Pp 
° 0:32 P 
41.6 | 48.1 y 0.35 P 
39.3 .6 | 48.0 4. 0:40 Pp 
39.4 | 44.7] 48.0 , 0:58 P}.. 
48.2 : PTD |e 
48.0] .. : Ip) ya eile 
48.0 ; 1:20 P|. <3 

- Ted 2uPalpe 
30.8 2:01 Pe}. 
80.9 2:10P]. 
31.0 2:38 P|. 42.0 
31.1 2742, Pills 41.5 
31.2 2:44 Pp]. . 3 9.6} 41.2 
31.8 DD OPPil ons ; 89.5 | 41.0 
32.0 8:03 P|. . 4) 40.5 
32.0 SEL OIeH ee: 39.0 | 40.2 
32.0 3a GPa. 0} 40.0 
31.9 S229) Palas 0 | 39.9 
31.9 3:50 Pie. 41 89.8 
81.9 B302,.P 5)... .9| 39.1 
81.9 ScOePrlha 3: 9} 39.0 
31.9 | 4A:DT P|. . .0| 37.4 
31.9 | 4:44 pP].. 3.8 | 36.9 


eo) 


39.6 
39.7 
39.7 
39.9 
39.9 
39.9 
40.0 
40.8 
40.5 
40.7 
41.8 
42.3 
42.5 


wo wo Oo 
WANA AS 
woo so 


“I 
oe 


Co 09 


GS 09 
rien es 
oOo =-l 


ee es 


wo oD 
> 0 


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» In & ww 6 


dS b> bo 
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wo CO 
oo © 
00 GO GO 


bo bo bs 


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RS Doe Ee CO dP & oO 


-1 -] 


+I 


“I -1 -1 -J 
Onto nk dS bw 


oo 


82 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


Air Temperature Humidity Air Temperature Humidity 


Hour. at on at 


Interval in 
Minutes 
Interval in 
Minutes 
Altitude 
above 
Valley. 


Altitude 


above 
Valley. 


at on in at on 
Kite. Hill. | Valley.| Kite. | Hill. 


in 
Kite. Hill. | Valley.| Kite. | 


1897. 
Jan, 2, : or, oF, OR. . | pect. ||| p. ct. age le or. or Crm ps.ct. |) ps 


4:59P|.. 3| 55.9] 36.7| 36.6] 49 | 90 25.7 | 84.6] 87.3] 57 
5:10P].. 56.1 | 36.7] 86.8] 48 | 90 | 8s tae 28.0 | 84.6] 37.2] 58 
5:20P]. .| € 47.9 | 36.7| 37.0] 68 | 90 
5:25 P|. . 3| 45.8 | 36.7] 36.9] 70 | 90 ‘ 28.0 | 82.1] 35.8] 35 
5:32 pe]. .| 527| 35.9] 36.7] 86.8] 76 | 90 | 8. 24.7 | 81.8} 35.2] 39 
5:35 P|. . 34.0 | 36.7| 36.7] 98 | 90 | 8. ght 24.0 | 81.8] 35.1} 40 
5:40 Pe]. .] § 35.1 | 36.7| 36.6] 98 | 90 | 8. 21.6 34.6| 48 
21.0 9| 34.3] 48 
weet ly me 20.3 8} 34.2] 44 
11:50 a1: ya Fey 30 18.0 71 349| 45 


PR OLeSe ar paca Be 15.9 | 30.7) 34.0| 45 
0:09 e| 3 | 900/102 30 a 
0:12 Pp ‘ wey (DY 3) 30 ee . By 40 
are ace 15.1 .2| 32.6| 39 
0:23 p 56 |—15.6 : i Ged) 
: 13.8 8| 31.9] 39 

0:26 p|. .|12341-16.5 | 3. 30 

0:44 ; 12.5 30 15.6 Adley) alles} 

Paral Sale ee. 13.7 .9| 81.1| 39 


hone fr at ace ie 13.1 | 28.7| 30.7] 37 
{TRE 7I_ 3.9 13.5 | 28.3| 30.4| 37 
15.5 | 28.1] 30.0] 38 
15.5 | 27.8| 29.6] 38 
17.0 | 27.1| 29.2! 38 
16.1 | 26.9| 29.1] 39 
16.5 | 26.8| 28.7] 39 
18.0 | 26.7| 28.7] 40 
19.9 | 26.2| 28.6 
21.4 |°25.9| 28.1] 44 


> 
(op) 
on 


sel el fe aia 
aIMwH So 


bo bS bo po 
> or i bo 
x 


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fon) 
bo oo BD © BS DO 
wo ow > Od OO OD OD OD 
DOM & & OO 


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29 


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+ 
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© coo =! 


Feb. 9. 
3:05 P 3! 29.8 48 
3:10 P 25.8 38. 48 
3:19 P| ¢ 2. 22.6 : 48 
3:25 P| 6 Uh a 38. 48 
3:30 P| 2 ( 19.5 
3:40 P| 3 : 26.1 k 48 


qo 0 ©. 


oo 
= 
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PHwwnwmnnanoawnp —& & 


bo 


Norr.— The second column gives the length of the interval, ending with the time given in the first 
column, that the meteorograph remained near the same altitude. The third column gives the mean altitude 
during this interval. The fourth and seventh columns, respectively, give the temperature and relative 
humidity recorded by the meteorograph at the end of the interval and at the time given in the first 
column. The remaining columns give synchronous observations at the ground. The summit of the hill is 
180 meters above the valley, which is 15 meters above sea level. 

The wind velocities ordinarily recorded by anemometers are about 18 per cent higher than the true velocities. 
The wind velocities given in Tables XVII. and XVIIL, and in the following Discussion, are corrected to true 
velocities. 


EXPLORATION OF THE AIR BY MEANS OF KITES. 83 


REMARKS. 


1896. 


April 8. Sky clear except for a few strato-cumulus. Tem- 
perature below normal but rising. Wind ENE; kites 
from NE at 445 meters, and from N above 700 meters. 

April 11. Sky partly covered with cirro-cumulus. Temper- 
ature above normal and rising. Wind W; kites from 
W at highest point. 

April 13. Sky partly covered with fracto-cumulus during the 
second flight. Temperature very high for the season. 
The wind was from WSW and backed to SSW and SW 
at the end of the flight. The kites entered the current 
from the W at 528 meters, and gradually shifted around 
to NW when 1,300 meters was reached. Electricity 
strong at the highest point. 

April 15. Sky clear except for a few cirrus. Temperature 
exceptionally high for the season. In descending, the 
kites shifted suddenly from a WSW to a S current at 
the altitude of 437 meters. Wind S; kites from SW at 
the highest point. 

April 23. Sky clear except for a few cirro-stratus and fracto- 
cumulus. Temperature above normal. Winds excep- 
tionally variable. Kites and instrument fell in trees on 
the hillside. Wind NW. 

April 24. Sky nearly covered with a sheet of cirro-stratus. 
Temperature slightly below normal and falling. Wind 
ESE; kites from E at 608 meters, from ENE at 677 
meters, and from NE at 856 meters. 

April 27. Sky about one tenth covered with cirrus. Tem- 
perature slightly below normal and rising slowly. Wind 
ESE; kites from SE at 266 meters, and from S above 
300 meters. 

May 4. Sky about eight tenths covered with cumulus. Tem- 
perature decidedly above normal. A cool wave on the 
5th. Slight shocks of electricity were felt when the kites 
were at altitudes exceeding 800 meters. Wind NW; 
kites from NNW above 600 meters. 

May 7. Sky clear. Temperature decidedly below normal, 
followed by a warm wave on the 8th and 9th. Elec- 
tricity became unpleasant when the altitude exceeded 
1,000 meters. Wind NE veering to ENF. 

May 8. Sky clear except for a few cirrus and fracto-cumulus, 
Temperature above normal, and rising rapidly. ‘The 
clock cylinder worked loose and the meteorograph record 
was lost after 3:30 p.m. Wind S; kites from SSW at 
highest point reached. 

May 9. Sky about seven tenths covered with cirro-stratus 
and alto-cumulus. Temperature decidedly above normal 
and rising. Kites gradually shifted to the right as they 
ascended. Near the ground the top kites were from S, 
at 673 meters they were from W, and at 1,300 meters 
from NW. At an altitude of about 700 meters the elec- 
tricity became so strong that it was necessary to ground 
the line. 

May 14. Sky about two tenths covered with strato-cumulus 


or flattened cumulus. Temperature above normal. Wind 
SSW. 


June 2. Sky partly covered with cumulus, rapidly decreasing 
in amount. Temperature near normal. Wind NW; kites 
continued from the same direction as the surface wind 
at the highest point. 

June 6. Sky covered with stratus during the early morning 
and most of the afternoon. This broke up and partly 
disappeared between 9 a.m. and 2p.m. Temperature 
below normal and falling. At 9:46 a.m., at an altitude 
of 470 meters, the kites entered the base of the fracto- 
stratus cloud. At 2:30 p.m. the lower kites entered the 
base of the stratus at a height of 424 meters, at 3 p.m. at 
a height of 422 meters, and at 4:53 p.m. were drawn out 
of the base of the stratus at an altitude of 412 meters. 
The instrument was above, and hidden by the cloud, 
during the greater part of the flight. Wind ENE; kites 
from E above 400 meters. 

June 11. Sky partly covered with cumulus. 
below normal. Wind WNW. 

June 12. Sky partly covered with high strato-cumulus. Tem- 
perature below normal, and stationary. Wind N. 

June 18. Sky nearly covered with alto-stratus, and rain fol- 
lowed during the night, Temperature below normal, and 
falling. Wind ESE backing to E; kites from SE above 
300 meters. 

June 17. Sky nearly covered with alto-stratus, with a few 
fracto-nimbus beneath. Temperature near normal. Elec- 
tricity on the line became strong when the kites reached 
an altitude of about 490 meters. Wind SSW. 

June 29. Sky partly covered with cumulus. Temperature 
normal. At 3:45 p.m., when the instrument was at an 
altitude of about 1,300 meters, the line broke at a splice, 
and the four upper kites and the instrument were carried 
away. After travelling nearly five kilometers, the lower 
kite caught, keeping the upper kites flying and the in- 
strument in the air until the kites were pulled down. 
No serious injury resulted. Wind WSW. 

July 8. Sky covered with stratus. Cool wave; tempera- 
ture 8° below normal. At 3:50 p.Mm., at an altitude of 
423 meters, the kites and instrument entered the cloud. 
Wind FE. 

July 10. Sky partly covered with cumulus and cirro-stratus. 
Warm wave; temperature about 9° above normal. No 
electricity noticed at the highest point, but slight shocks 
felt in the descent when the instrument was at an altitude 
of about 785 meters. Wind WSW. 

July 20. Sky covered with alto-stratus and cumulus, chan- 
ging later to strato-cumulus. Temperature near normal 
and rising. At 10:38 a.m., and at an altitude of 841 
meters, the kites entered the base of a fracto-cumulus. 
After this, cumulus continued driving over and hiding 
the kites occasionally. Electricity was very strong at the 
highest point. Wind SW backing to SSW. At 1:50P, 
at the altitude of 988 meters, when descending, the kites 
suddenly shifted 28° of azimuth to the left. 

July 22. Sky nearly covered with a sheet of alto-cumulus, and 
partly covered at a lower level with a sheet of strato- 
cumulus. Temperature above normal. At 2:33 p.m. the 


Temperature 


84 BLUE HILL 


kites entered the base of the strato-cumulus at an altitude 
of 605 meters. At 5:18 P.M., at an altitude of 670 meters, 
the meteorograph was drawn below the base of the strato- 
cumulus. During most of the flight the instrument was 
occasionally hidden by the low clouds. Wind SSW back- 
ing to S. 

July 25. Sky clear except for a few cumulus. Temperature 
near normal but falling rapidly, due to the approach of a 
cool wave. Two flights were made. In the first one the 
line was pulled in to remove a defective kite. Wind 
WNW veering to NW; during the two flights the kites 
continued from the same direction as the surface wind. 

Aug. 1. Sky clear except for a few cirro-cumulus. Temper- 
ature below normal. At the highest point reached elec- 
tricity was moderately strong. In descending, one of the 
bolts on the drum was broken by the crushing strain of 
the wire. The wind backed from W to S during the 
ascent. The kites shifted rapidly to the right while as- 
cending, and at the highest point pulled from NW when 
the surface wind was from S. 


Aug. 17. Sky partly covered with cumulus. Temperature 
near normal. Electricity became strong at 900 meters 
altitude. A sea breeze set in on the hill as the kites 


reached the ground. Wind NNW veering to N; kites 
shifted to the right as they ascended, and at 900 meters 
were 16° of azimuth to the right of the surface wind. 

Aug. 22. Sky partly covered with alto-cumulus and broken 
nimbus or strato-cumulus. Light sprinkles of rain during 
the ascent. Temperature near normal, and rising. The 
instrument entered the base of the nimbus at an altitude 
of 1,207 meters. Wind SSW; kites shifted to the right 
as they ascended, and above 1,100 meters were 380° to 
86° of azimuth to the right of the surface wind. 

Aug. 26. Sky partly covered with cumulus. Temperature 
near normal. Electricity on the line was strong when 
the instrument was above 1,300 meters. Wind S back- 
ing to SSE; kites shifted to the left as they ascended, 
and at 1,400 meters were 25° of azimuth to the left of 
the surface wind. 

Aug. 31. Sky partly covered with fracto-cumulus, which 
changed later to cumulo-nimbus, with light showers in 
the afternoon. Temperature below normal. At 1,273 
meters the instrument entered the base of the fracto- 
nimbus cloud. After the highest point was reached, and 
about 600 meters of wire wound in, the wind became too 
light to support the kites, and the entire line of them 
settled to the ground. The instrument and upper kites 
were found uninjured 2,500 meters from the Observatory. 
Wind SW;; kites shifted to the right as they ascended, 
and at 2,000 meters were 58° of azimuth to the right of 
the surface wind. 

Sept. 8. Sky covered with cirro-stratus. Temperature below 
normal. Pull of the kites on the line unusually steady. 
Wind NE and ENE;; kites shifted to the right as they as- 
cended, and at 1,300 meters were 20° of azimuth to the 
right of the surface wind. 

Sept. 11. Sky clear except for a few cirrus. A warm wave ; 
temperature about 12° above normal. Wind S; kites 
shifted to the right as they ascended and at 600 meters 
were about 40° of azimuth to the right of the surface 
wind. 


METEOROLOGICAL OBSERVATIONS. 


Sept. 16. Sky nearly covered with strato-cumulus. Temper- 
ature below normal. Moderate shocks of electricity felt 
when the meteorograph reached 520 meters. ‘The me- 
teorograph entered the base of the cloud at an altitude of 
590 meters, in the ascent, and came out of the cloud, in 
the descent, at 486 meters. Wind ENE; kites 38° of 
azimuth to the right of the surface wind at 576 meters. 

Sept. 17. Sky nearly covered with strato-cumulus. Temper- 
ature near normal. When the altitude of about 1,000 
meters was reached, the electricity became unusually 
strong. The kites and instrument entered the base of 
the strato-cumulus at a height of 840 meters. The kites 
were drawn out of the base of the cloud, in the descent, 
at an altitude of 900 meters. At 762 meters, in descend- 
ing, the kites suddenly shifted to the left. Wind SSW 
veering to SW; kites 44° of azimuth to the right of the 
surface wind at 1,000 meters. 

Sept. 18. Sky partly covered with cirrus, Temperature 
above normal. Wind NW; kites some 10° of azimuth 
to the right of surface wind at 900 meters. 

Sept. 19. Sky nearly covered with dense cirro-stratus and 
low strato-cumulus. ‘Temperature near normal but fall- 
ing. The kites were in the cloud, and the meteorograph 
remained suspended in the base of the strato-cumulus from 
8:53 to 4 p.m. at an altitude of 403 to 425 meters. Rain 
began at 6:35p.m. Wind SSW;; kites 35° of azimuth to 
the right of the surface wind at 400 meters. 

Sept. 20. Sky clear except for a few fracto-cumulus. Tem- 
perature below normal. At 1,000 meters the electricity 
became strong. Wind WNW;; kites 45° of azimath to 
the right of the surface wind at 2,200 meters. 

Sept. 24. Sky nearly covered with strato-cumulus. Temper- 
ature below normal but rising rapidly. Wind very 
variable, and it was difficult to maintain the kites in the 

Wind NW and WNW. 


air. 

Sept. 25. Sky partly covered with cirro-stratus. Tempera- 
ture near normal. Wind SE veering to SSE. 

Sept. 29. Sky nearly covered with stratus. Temperature 


above normal and rising. Kites and meteorograph en- 
tered cloud at an altitude of 930 meters. The clock 
cylinder of the meteorograph was jerked off and the 
record lost after 5:40 p.m. Wind SE; kites shifted to 
the right as they ascended. 

Oct. 6. Sky covered with low strato-cumulus. Temperature 
considerably below normal. At 11:25 a.m. the kites and 
instrument entered the base of the strato-cumulus at an 
altitude of 471 meters. At 11:45 a.m. instrument in the 
lower edge of the cloud at an altitude of 513 meters. At 
11:54 instrument re-entered cloud at an altitude of 519 
meters. At 0:42 Pp. mM. instrument in the base of the cloud 
at an altitude of 602 meters. Wind NNE; kites shifted 
to the left as they ascended, and above 500 meters were 
80° to 34° of azimuth to the left of the surface wind. 

Oct. 8. Sky partly covered with cumulus at the beginning of 
the flight, which later changed to strato-cumulus, covering 
almost the entire sky during the afternoon. Temperature 
decidedly below normal and falling slowly. The meteoro- 
graph entered the cloud at 1:58 p.m. at an altitude of 
1,858 meters. ‘The meteorograph sank below the base 
of the clouds at 2:59 p.m., 2:58 p.m., and 3:34 p.m.; 
but during much of the flight it was hidden by the 


Oct. 31. 


Noy. 18. Sky covered with a uniform sheet of stratus. 


Nov. 380. Sky covered with stratus. 


EXPLORATION OF THE AIR BY MEANS OF KITES. 


85 


clouds, and was only seen occasionally through the breaks | Dec. 12. Sky partly covered with cirrus. A warm wave; 


between the clouds. In the morning, after 11 a.m., the 
kites were wound in to remove a defective kite, so that 
only 700 meters of line remained out. At 0:31 P.M. a 
second ascent was begun. At 1:45 p.m. the kite line was 
grounded on account of the intensity of the electricity 
on the line. Wind WNW;; kites continued to shift to 
the right throughout the flight. 


Sky partly covered with cumulus decreasing in 
amount. A warm wave; temperature about 20° above 
normal. Electricity on the line moderately strong at 


the highest point reached. The instrument was partly 
torn from its fastenings by the diving of the kites, and 
the record lost after 4:50 p.m. Wind WNW and NW; 
kites shifted to the left as they ascended, and above 1,000 
meters were 30° of azimuth to the left of the surface wind. 


Nov. 17. Sky clear at the beginning of the flight except for 


a few fracto-cumulus; but these soon changed to strato- 
cumulus, which partly covered the sky. A warm wave; 
temperature nearly 20° above normal. At 8:31 P.M. the 
meteorograph and upper kites entered the base of the 
cumulus, at an altitude of 1,572 meters, but the kites 
immediately afterward dived and fell below the cloud. 
Wind W and WNW; kites shifted to the right as they 
ascended, and above 1,200 meters were 22° to 24° to the 
right of the surface wind. 

Tem- 
perature lower than on the 17th, but still considerably 
above normal. On account of the light wind, one kite 
was sent up about 500 meters before attaching a second 
kite and the meteorograph. The meteorograph entered 
the base of the stratus at 0:31 p.m., at an altitude of 515 
meters, and continued visible in the base of the cloud 
until 0:47 p.m., when the wind became light and the kites 
sank to the ground. During the flight, from the time 
the meteorograph was attached until it was taken off, the 
highest kite remained in a strong upper current from the 
southwest, while the lower kites were in a current from 
the northeast. As a result of this pull on the line from 
opposite directions, it was carried up at a very steep angle. 
The meteorograph did not reach the upper current. 

A cold wave; tempera- 
ture 8° to 10° below normal and falling rapidly. The 
kites did not reach the stratus clouds, the wind being too 
light above to lift the kites. At 11 a.m. a break occurred 
in the cloud, when it was seen that the top of the cloud 
was moving from the southwest across the face of the 
sun, while the base of the cloud was from the north or 
north-northeast. The wind was N and NNW throughout 
the flight. The altitude of the cloud was found, by re- 
flected light during the evening, to be about 880 meters. 


Dec. 15. 


dan. 


Jan. 


Feb. 9. Sky partly covered with fracto-cumulus. 


Feb. 10. Sky clear except for a few fracto-cumulus, 


temperature above normal and rising. Two flights were 
made, one in the morning, the other in the afternoon. At 
the highest point reached in the afternoon, the meteoro- 
graph entered a warm and very dry curreut from the 
west. Wind SW. 

Sky covered with strato-cumulus. Temperature 
below normal, and falling. At 2:23 p.m. the kites, with 
the meteorograph, entered the base of the strato-cumulus 
at an altitude of 710 meters, and became invisible, except 
at 2:26 to 2:27 p.m., when they were seen in a break in 
the clouds. At 2:36 p.m. the kites had fallen below 
the cloud. Wind ENE; kites shifted to the right as 
they ascended and at 600 meters were 26° of azimuth 
to the right of the surface wind. 


1897. 


2. Sky covered with stratus, which cleared away be- 
tween 2 and 5 p,M., leaving the sky partly covered with 
cirrus. Temperature above normal and rising rapidly, 
due to the approach of a warm wave. The kites and 
meteorograph entered the base of the stratus at 11:55 a. M., 
at an altitude of 522 meters. After 0:01 p.m. the kites and 
instrument were hidden by the cloud until it began to 
break away at 1 p.m. The altitudes during this time 
were taken from the barograph. Electricity quite strong 
at an altitude of 160 meters. At greater altitudes it be- 
came weaker. After passing through the stratus at a 
height of about 700 meters, the meteorograph showed a 
remarkable rise in temperature and a fall in humidity. 
Wind SW; kites shifted to the right as they ascended, 
and entered a current from the west at about 700 meters 


altitude. 
19. Sky clear. A cold wave; temperature 20° below 
normal. The wind was so strong at the highest point 


reached by the kites that it was considered wise not 
to go higher. Wind NW and WNW/;; kites continued 
throughout the flight from nearly the same direction as 
the surface wind. L! 

Temper- 
ature above normal but falling. Wind NW; kites contin- 
ued throughout the flight from nearly the same direction 
as the surface wind. 

Tem- 
perature near normal but falling rapidly, due to the 
approach of a cold wave. Electricity weak, and only 
observed at the highest point reached. Wind NW;; kites 
continued from nearly the same direction as the surface 
wind up to about 1500 meters, then shifted suddenly 18° 
of azimuth to the right. 


Note. — The direction of the wind is that of the surface wind on Blue Hill, and the altitudes are above the Valley 


Station, 180 meters below the summit of the Hill, unless otherwise stated. 


86 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


TABLE XIX. 


SPECIMEN OF OBSERVATIONS AT THE WINDLASS. 


Aucust 26, 1896. 


Meteorograph. Meteorograph. Litie Meteorograph. Meteorograph. 


out, 


Time 
P.M, 


Line 
out. 


Line La 
out. = 
A 
4 


Alt. 


Line 


t. 
si Alt. 


meters. 
1500 
500 ; = 


cg. meters. 
5:19 | 2000 
6:21 ce 
5:22 . 
5:24 ds 
5:25 
5:26 
0:27 SS 
5:35 ?| 2700 
5:44 se 
5:45 be 
5:46 Ke 
5:48 sé 
5:06 | 8400 
6:01 
6:08 
6:04 
6:05 
6:06 
6:07 
6:10 
6:11 
6:18 


meters. 


3400 


meters, | 


bo =| Pull of 
OS® | Kites 


39.0 
88.8 
38.8 
38.5 
38.6 
38.4 
38.6 
30.5 
31.4 
31.5 
31.6 
31.9 
25.0 
27.0 
26.6 
26.4 
26.2 
26.7 
27.0 
26.4 
26.7 
26.5 


36.0 
36.5 
37.8 
36.8 


37.2 


bo 


28.4 
30.6 
31.9 
b4.4 
33.5 
32.8 
33.6 
34.5 
33.0 
34.9 
39.2 
35.4 
35.5 
37.0 
38.5 
38.7 


~ 
to 


bo 


~ 


He CO b 


| 
| 
| 
| 
| 
| 


> oO 
bo t 


b> BD co OS BD BD 


> ret 


bo 
re 


to by 


ww v9 bo 


= bo 


Norr. — The line out is the length of wire from the windlass to the meteorograph. Minus azimuths indicate that the 
kites shifted to the left as they ascended. 


REMARKS. 


From 3:50 to 3:55 Pe the kite meteorograph swung from the too dark to see the meteorograph after 6:42 p, and no 


tripod wire for comparison with the Observatory instru- 
ments. 4:02pe the kite meteorograph left the ground 
lifted by a six-foot and a nine-foot modified Eddy kite. 
4:40 p electricity first noticed on the line. 4:52 Pr added 
a six-foot kite and let out line. 5:27 p added a six-foot 
kite and let out line. From 6:03 to 6:15 Pe the angular 
altitudes were read on the top kite, 35 meters beyond 
the meteorograph. These readings were made simul- 
taneously with theodolite observations at the ends of a 
2590 meter base line, the object of which was to deter- 
mine the height of the kite by triangulation. It became 


further readings of the angular altitudes were possible. 
6:45 P electricity strong. 8:10 P began to reel in the line. 
9:54e the meteorograph reached the ground and was 
hung on the tripod from 9:56 to 10:09 e for comparison 
with the Observatory instruments. 


The wind was from the S at the beginning of the flight, 


but backed to the SSE about 6 P.M. and continued from 
that quarter until the end of the flight. The kites shifted 
to the left as they ascended, as shown by the readings in 
the azimuth columns. The wind velocity varied between 
4.5 and 9.6 meters per second during the flight. 


EXPLORATION OF THE AIR BY MEANS OF KITES. 87 


III. — Discussion oF THE RECORDS. 


By H. Hretm CuiaytTon, 


ACCURACY OF THE OBSERVATIONS. 


Tue value of the results derived from the kite meteorograph depends largely 
on the accuracy with which the altitudes of the instrument, from moment to 
moment, are determined ; therefore this accuracy demands first consideration. 

Fortunately, the errors in determining altitude are found to be small, and affect 
the results to no greater extent than the instrumental errors of the meteorograph 
itself affect them. Our usual method of finding the altitude, when the meteoro- 
graph is visible, is by the formula 


A = (sin jy U2; 5 


7 


in which A represents the altitude; h, the angle above the horizon read by an 
altazimuth instrument placed near the reel; /, the length of line from the reel to 
the meteorograph, read from the dial; and wz, a constant quantity determined 
experimentally as a correction for the sag of the line, and for other incidental 
errors. If the meteorograph is not visible, as, for example, at night, or when 
hidden by a cloud during the day, the altitudes are taken from the barograph 
trace, which is arranged to give altitudes graphically for the mean air temperature 
of 32°F. These altitudes, corrected for the observed air temperature, are taken as 
the true altitudes. When the fall or rise of temperature with height above the 
ground is shown by the meteorograph in its ascent to be uniform, the mean of 
the temperatures recorded simultaneously at the meteorograph and at the ground 
is taken as the mean temperature of the air column, and is used in the corrections 
of the altitudes by the barometer. But when the change of temperature with 
height is not uniform, as, for example, when the temperature rises till a certain 
altitude in the air is reached and then falls with increase of altitude, the means 
of the temperatures at the extreme points are taken. These means are then 
weighted in proportion to the lengths of the air column between these points, in 
order to get the mean temperature. 


88 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


To describe the process more explicitly. The mean of the temperature recorded 
at the ground and at the place of highest temperature is taken; then the mean 
of the highest temperature and that recorded at the kite is taken; the two means 
are weighted in proportion to the vertical distance in each case; then, from these, 
a final mean is obtained which is used for the correction of the height given by 
the barometer. The chief error in taking the altitudes from the barograph arises 
from the contracted scale necessarily used, and from the breadth of the trace due 
to the vibration of the recording pen, caused by the kites. On this account, as 
well as on account of the instrumental error of the barograph and the uncertainty, 
at times, of the proper temperature correction, the error of getting the altitude 
from the barograph is considerably greater than by the method of using the angular 
altitude of the meteorograph and the length of line from the reel. 

To determine the accuracy of the two methods by a third and independent 
method, and to obtain the correction x for sag of line, etc., in the first method, 
simultaneous measurements of the altitude of the kite meteorograph, or an adjacent 
kite, were made, from time to time, with the theodolites used for the measurement 
of cloud heights. In most of these measurements the length of the base line was 
1,178 meters; but in two cases, August 26 and December 12, 1896, the base line 
was 2,590 meters in length; and in the first two cases, August 26 and 27, 1895, 
it was 100 meters. After correcting for instrumental errors, the formula used for 
computing the height is 
2, = b sin a, (cosec a; — az) tan hy 
% = (b sin a, (cosec a, — az) tan hy) — C3 
in which a, and h, and a, and fA, are the azimuths and the angular altitudes of 
the kite meteorograph observed from the two stations respectively ; 4 is the length 
of the base line; C is the difference in level between the two ends of the base 
line; 2, and z are the computed heights by the two methods; and Z, which is 
assumed to be the correct height, is the mean of z, and 2). 

In Table XX., column 1 gives the altitudes in meters computed from simultaneous 
theodolite measurements at the ends of a base line. Column 2 gives the altitudes 
computed from the formula 

Z = (sin A) J, 
in which sin / is the angular altitude of the meteorograph or of a kite measured from 
the reel, and 7 is the length of line to the object. Column 3 gives the height com- 
puted from the barograph carried by the kites. This includes a correction for the 
mean temperature of the air column, and a correction for the height of the kite 
above the barograph when a kite was selected for measurement. In a few cases, 


EXPLORATION OF THE AIR BY MEANS OF KITES. 89 


TABLE XX. 


COMPARISON OF ALTITUDES BY DIFFERENT METHODS. 


eh 2 4 5 2 3 a 5 
Alti- | Alti- - Column 2 Column 3 ‘i Alti- Alti- Column 2 Column 3 
tude | tude minus minus tude tude minus minus 

by by Column 1, Column 1, by by Column 1. Column 1, 
Theod-| Angle aro= |__| ——____—__ Theod-| Angle | Baro- 
olites. | and olites. and | graph, 


. ‘i Per Per : M Per .| Per 
Tite. Meters. Sone Meters.| Got. Line. eters, Gent, | Meters. Cent. 


| 
meters.|meters.|meters, 1896. meters. | meters. | meters. 


8:58 e| 400} 894]... soe |e ep wute | 4:50 Ph1736) 1832)... |4+-96 
5:09 p| 452) 468]... ee A, 4:32 p| 1759 | 1821]. . .|+62 
HlOie 463) 481)... ee homens 4:33 p| 1772/1826] .. .|/+54 
Means} 488] 448]... cB Faunee street 4:34 p|1782|1837] . . .|+55 
Aug. 27} 5:28 e| 611} 620]... AWE Es Perens 4:36 P| 1878|1892|.../+14 
1896. 4:37 p| 1870 | 1983]. . .|+63 
June 6/10:094] 368] 365)... Ses | wee Means} 1800 | 1857] . . .|/+57 
TOM Oes OL | 380). 2. i Perea Cor 4:38 p| 1961/1982] .. ./+21 
TOMeAne S30 a45i\2, 5). Syeik en | savetae 4:39 p | 1984 | 2056] . . ./+122 
RUA OWA 20"! BBO le) es Ss) ot || sane 4:40 p | 2010 | 2080] . . .|+70 
Means | 353] 355]... Of apres lenromee 4:41 p| 2015 | 2065) . . ./+50 
Ole oo4 | 578 ile. ae Ae ein 4:42 p | 2031 | 2065} . . ./+84 
0:22 p| 596} 604]... een race. 4:43 p| 1981] 2046] . . ./+65 
0:25P| 574} 586)... : PBT. cihhe tec Means! 1989 | 2049 + 60 
0:26 p| 590} 598]... Re ills icicy 6:07 P| 1501 | 1552 +51 
O2teiolOh 616)... <fgee|aae 6:10-P | 1474 | 1521 +47 
Means| 587| 597|... iat eee 6:11 ©) 1493 | 1537 +44 
Beoterye ote. S53\- . Ora’. aa ome 6:18 Pp | 1492 | 1526 + 3-4 
BOE COO! | B21 | we. « ree | once 6:14 P| 1486 | 1488 +52 
SeP eto) 163 | «0 33 careers| sh oe 6:15 p | 1478 | 1526 +48 
3:29 P| (40). 788)... ie CN eae Means| 1479 | 1525 +46 
SSO ve |) PROB aw BX0N Aner reed Gat 3:00 P| 605} 609 + 
Means! 761} 781 ; om 3:01 ep| 620} 616 = 
June 29| 3:19 p|1031 /1070 ot 3:02 eP| 620] 626 + 
3:20 p |1046 |1085 é 3:03 pe} 619] 612 —_ 
8:21 p |1035 |1060 é 3:06 P|} 601} 607 
Means |1087 |1072 a Means) 613] 614 
S20 -e | fal | 734 
8:28 P| 729° 732 ‘ 3:51 PrP) 925} 950 
3:29 P| 712| 726 y 3:02 P| 918} 945 
3:30 P| 714] 728 3:03 P| 924) 945 
3:31 P| 682| 686 3:54 P| 917) 945 
Means | 714| 721 Means| 921) 946 


the highest kite was selected for measurement, because it was impossible to see 
the meteorograph from one of the theodolite stations. Column 4 gives the differ- 
ence between column 2 and column 1 in meters and in percentages of the height. 
Column 5 gives the difference between column 3 and column 1. In the first two 


90 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


flights in 1895, and on June 19, 1896, no barograph was carried by the kites. 
On June 6 and August 1, 1896, the trace made by the barograph at the time of 
the measurements was too faint to be read, although the loss of such records is 
rare. Comparison of column 1 and column 2 shows that the agreement is closer 
than with column 3, notwithstanding the fact that no correction is made in column 
2 for the sag of the line. By classifying, according to height, the mean differences 


between column 2 and column 1, we obtain 


TABLE XXI. 


COMPARISON OF MEAN ALTITUDES OF THE KITE METEOROGRAPH. 


Mean Difference between Difference in Di ; 

Altitude aiece mites and jtnele Per Cent for each | Per Boars gach 
by of Meteorograph am 200 Meters. 

Theodolites. Length of Line. oak peo M stoke. 


meters. meters. per cent. 
June 353 + 2 +0.6 
Aug. 438 +10 +2.3 
June 587 +10 sim lai 
Aug. 611 + 9 +14 
Dee. 1: 613 + 1 +0.2 
July 714 saa + 1.0 
June 761 + 20 +2.6 
Jan. 2 921 |} +25 2.0 
June 1037 +35 +3.4 
Aug. 1479 +46 +31 
Aug. 1800 +57 ose 
Aug. 1989 + 60 +300 
Mean Sell 


This table shows that, in the average, the altitudes computed from the angle and 
the length of the line exceed the altitudes measured by theodolites about 2 per cent 
of the height. In this difference are included such errors as may exist in the recording 
apparatus, as well as the error Arising from the sag of the kite line. The dial for record- 
ing the amount of line unrolled was tested by running lengths of 100 meters over the 
registering wheel; and the indications were found to be correct within less than 1 
per cent, except in the earliest apparatus, in which the error was somewhat greater. 
The circles of the altazimuth instrument used for measuring the angular altitude of 
the kites were divided to half-degrees, and were read to tenths of degrees. The 
instrument was subject to slight errors; but these were made as small as practicable. 
Hence the excess of 2 per cent is believed to be due chiefly or entirely to the sag 


of the line. 


EXPLORATION OF THE AIR BY MEANS OF KITES. 91 


Professor C. F. Marvin, in his mathematical analysis of the forces acting on the 
kite and line, computes that the percentages of slack (or sag) under varying conditions 
practically attainable range between 0 and 5 per cent, averaging somewhat less than 
2 per cent (Monthly Weather Review, U. 8. Weather Bureau, July, 1896, p. 252). 
With a number of kites on the line, as in tandem flying, the amount of sag would 
probably approximate thisaverage. The results in Table XXI. show an increase in 
the percentages of difference between the heights by the two methods with increas- 
ing altitude. This may be due to errors in the methods of measurement, or to an 
increase in the amount of the average sag in the line. The increase, as shown by 
the last column in Table XXL, is about 1.6 per cent for the 1,500 meters between 
250 and 1,750 meters, or the same between 400 and 1,800 meters, as shown by the 
fifth column. In other words, it is about 1 per cent for each 1,000 meters of ascent, 
so that, taking the excess of altitudes computed from the kite line as 1.5 per cent 
at 500 meters, it would be 2 per cent at 1,000 meters, and 5 per cent at 3,000 
meters. In practice, it was decided to apply a correction of 2 per cent for altitudes 
below 1,500 meters, and a correction of 3 per cent for altitudes above this distance ; 
so that the value of x in the formula becomes 0.98 in one case, and 0.97 in the 
other. 

Returning now to Table XX., and subtracting 2 per cent from all the individual 
percentages in column 4 where the height was less than 1,500 meters, and subtracting 
3 per cent where the height was above this distance, the average of the resulting 
figures is found to be +1.3 per cent. From this, according to Peters’s formula, the 
probable error is about +1 per cent for any altitude computed from the formula 


Z = (sin h) lx. 


This, however, includes the probable error of the theodolite measurements., If we 
assume the latter to be 0.5 per cent, the probable error in the measurements by the 
line and angle is +0.9 per cent. Hence the altitudes computed by the above formula, 
which comprise most of the observations, have a probable error of 1 per cent in 
round numbers, when the values of « given above are used. The probable error of 
the altitudes, measured by the barograph, is larger. From the residuals in Table 
XX. it is found to be between 3 and 4 per cent of the computed height. 

The thermograph records are liable to several errors. The chief error arises 
from the exposure of the thermograph bulb. In the first thermograph, shown in 
Plate VIUI., used from August 4, 1894, to September 21, 1895, the bulb was pro- 
tected from insolation and radiation by arching a sheet of aluminium over the bulb, 
and enclosing the entire instrument in an inverted basket, through which the wind 


92 BLUE HILL METEOROLOGICAL OBSERVATIONS, 


could blow freely. Comparisons between the standard thermometer in the Observa- 
tory shelter and the records of the instrument, when swinging from the kites within 
30 meters of the ground, showed that this exposure was fairly satisfactory. 

In the meteorograph used from November 16, 1895, to April, 1896, and occa- 
sionally in May and June, 1896, (Plate IV. Figure 30,) the thermograph bulb was 
exposed beneath the instrument, and was well shaded, but the temperature was 
found to be considerably raised by insolation, perhaps on account of conduction 
of heat through the case. However, it is assumed that, at the small altitudes 
reached by this instrument, the insolation was virtually the same as near the 
ground, and that the correction required to reduce the readings to that of the 
standard thermometer in the shade, found when the instrument was near the ground 
and in full sunlight, can be applied to the records obtained at greater altitudes, in 
order to get the true air temperature. In other words, the condition remaining the 
same, it is assumed that the instrument recorded the correct fall or rise of tem- 
perature between successive altitudes. Hence the temperatures corrected to the 
Observatory standard by applying a correction determined at the beginning and 
end of each flight of the kites are given in Table XVII. 

The records of the third meteorograph (Plate VIII.) begin with Table XVIII. 
With this instrument, a screen which is described by Mr. Fergusson and shown 
on Plate IV. Figures 35 and 36, was adopted after a number of trials of different 
forms, and it gives very satisfactory results. Two methods of testing the exposure 
were tried : — 

1. The meteorograph was hung from a wire extending from the top of the 
Observatory to an adjacent tripod; near noon, the point of support was moved 
backward and forward a few feet, so that the instrument was for a few minutes 
in full sunshine, and then for a few minutes in the shadow of the Observatory, but 
with scarcely any other change in environment. In both cases, the instrument was 
freely exposed to the breeze. The mean results of a number ‘of cases show that 
the temperature averaged very slightly lower in the shade than in the sun. 

2. The instrument was hung from the wire 2 or 3 meters above the ground in 
full sunlight, and in a moderate wind; and the records were compared with 
the readings of a standard Fahrenheit thermometer in the thermometer shelter 
used at the Observatory. Following are the results of such a comparison, made 
August 13, 1896 :— 


Time,r.w. 2:05-2:06 2:07 2:08 2:09 9:10 241 212 213 214 215 2:18 
Thermometer 76°.5 76°.4 76°.8 76°.5 76°.7 76°.5 77°.0 76°.9 76°.7 76°.4 76°4 76°.0 
pein bree 76°.0 76°.0 76°.3 76°.9 76°.7 76°.7 76°.3 76°.1 76°.1 76°.1 75°.4 
gre 


EXPLORATION OF THE AIR BY MEANS OF KITES. 93 


Both instruments were corrected for instrumental errors. The results show as 
close an agreement as could be expected in the case of instruments separated by a 
short distance. Comparisons were also made with Assmann’s aspiration thermometer 
with almost identical results. It is customary to suspend the kite meteorograph on 
this wire, in the position described above, for a few minutes before and after every 
ascent, for the purpose of comparing its records with those made by the recording 
instruments at the Observatory. This is necessary because the jerking of the kites 
sometimes displaces the pen, and the irregular cutting of the record sheets and 
their hygroscopic character make the position of the datum line uncertain. The 
differences found between the standard instruments and the records of the kite 
meteorograph are applied as corrections to the latter. In this way, numerous 
comparisons were made. When the comparisons were made in full sunshine near 
the warmest part of the day, and were made also on the same days after sunset, 
the results show that the bulb of the kite meteorograph was well screened from 
insolation. If the comparisons were made first when insolation was in excess, and 
then when radiation was in excess, it is assumed that the mean of the two series 
gives the instrumental error of the kite meteorograph. After applying this correc- 
tion for instrumental error to the thermograph, the following figures show the 
differences, in degrees Fahrenheit, between the readings of the kite thermograph 
and the readings of the Observatory thermograph exposed in the usual shelter and 
corrected to the readings of a standard thermometer : — 

“ee” (2:05 P+0°.1 oe { 3:55 P+0°.2 9:30 0 +0°.1 (2:00 P 0°.0 

AUB} siz de1 AME 257 10002095 OB ose geo Nove 3 Leore 0% 

1897. 


jn Be ol, Feb. 10 4 3:00 p+0°.9 


5:54 p—0°.6 6:53 p—0°.9 

The sign + indicates that the corrected reading of the kite thermograph was 
higher than the standard ; the sign — indicates that it was lower than the standard. 
The results show a slight amount of heating by insolation, but I think this is 
partly explained by reflection of heat to the bulb from objects near the ground. 
A final test of the exposure is found in the fact that, at altitudes exceeding a 
kilometer, almost exactly the same temperatures were recorded at the same 
altitudes before sunset as after sunset. This will be brought out subsequently in 
the discussion of the diurnal period. 

The next error of importance to which the thermograph record is liable is the 
sluggishness of the thermometer. Numerous tests, made during the winter by 
taking the thermograph from a heated room into the open air, showed that the 
thermograph trace fell some 20° to 30° F., and recorded within two or three tenths 


94 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


of a degree of the true air temperature within about three minutes. At the end of 
five minutes it assumed, virtually, the air temperature. When the fall of tempera- 
ture was less, or the winds were high, these intervals were somewhat shortened. 
Hence, in practice, it is our custom, after letting out a certain amount of line, to 
allow the kites to rise to their maximum angular altitude. Then, when they have 
remained as nearly stationary as practicable from three to five minutes, they are 
sent higher by letting out more line. ‘This serves also as an excellent check on the 
time errors of the meteorograph, and makes it possible to connect the temperature 
readings and the altazimuth readings, with comparative certainty. The temperature 
is read from the record at the end of the intervals, when the kites are nearly sta- 
tionary. When the vertical motions of the kite are very great, the intervals when 
the meteorograph is nearly stationary for a few minutes are selected from the baro- 
graph record. These intervals can usually be connected with readings of the alt- 
azimuth instrument, in order to determine the altitudes with greater accuracy. 

When records of wind velocity were obtained, it was customary to leave the kites 
near the same altitude for 10 to 15 minutes. To test the accuracy of the anemometer 
record, the meteorograph was suspended from the kites, and at the beginning or end 
of each ascent it was maintained, if possible, at the approximate height of the Obser- 
vatory anemometer, long enough to record the velocity of the wind. The duration 
of the suspension was, in most cases, about 15 minutes; and the true velocities ranged 
from 4.5 to 10.3 meters a second, or from 10 to 23 miles per hour. The average 
velocity of the 20 comparisons is 7.8 meters per second (17.4 miles per hour). In the 
average, the kite anemometer differed from the Observatory anemometer 0.5 meter 
per second (0.6 mile per hour). This difference is between 3 and 4 per cent of the 
total velocity, — a difference not uncommonly found between two similar anemome- 
ters placed near together on the same tower. 

The errors of the record of relative humidity, compared with a psychrometer, 
average about 5 per cent. There are individual errors of 10 per cent or more. 
The hairs in the instrument are very sensitive to the jerking of the kites, and were 
repeatedly thrown out of place. Thus the records of the hygrograph are less satis- 
factory than the others; but the results, corrected for instrumental errors, are believed 
to be approximately correct. They at least show the directions of the changes in hu- 


midity, if not the exact amounts. 


RESULTS FROM THE RECORDS OF THE ANEMOMETER. 


The records of the anemometer in the meteorograph which was lifted by the 
kites show that, as a rule, the wind increased steadily as the kites ascended. The 


EXPLORATION OF THE AIR BY MEANS OF KITES. 95 


average difference between the wind at the kite and the wind on Blue Hill, for 
each increase of 100 meters above Blue Hill, is shown in the following table. 


TABLE XXII. 
INCREASE OF WIND VELOCITY FOR EACH 100 METERS ABOVE BLUE HILL. 
50 150 250 850 450 550 650 750 850 


Height above Blue Hill in meters to to to to to to to to to 
1500 =) 250 350 450 550 650 750 850 950 


Average increase | meters per second 0.8 1.0 1,3 1.6 0.9 0.2 3.7 5.7 iy 
in wind velocity ( miles per hour 1g 2.2 2.9 3.5 2.0 0.4 8.2 12.7 3.8 
Numuemonrecords >: . . . . . 5 30 26 19 18 7 7 4 3 4 


The rate of increase shown in this table for altitudes above 450 meters is irregular 
on account of the small number of observations. Between the average heights of 
100 and 400 meters, the rate of increase of velocity for each 100 meters of greater 
altitude, was 0.3 meter per second, or 0.6 mile per hour. The rate of increase per 
100 meters, found from the measurements of clouds in 1890 to 1891, for altitudes 
from 2,000 to 12,000 meters, was 0.27 meter per second in summer, and 0.65 meter 
per second in winter, making the mean 0.46 meter per second for the year. The 
records got with the kites were distributed throughout the year. Hence the results 
indicate that the rate of increase of velocity with altitude immediately above Blue 
Hill is less than that in the cloud levels at a greater height. Perhaps this may be 
caused by the influence of the hill. The excess of the average wind velocity recorded 
on Blue Hill over that recorded at the Weather Bureau station in Boston (ten miles 
north of Blue Hill) is 3.1 meters per second. The difference in level between the 
anemometers is 144 meters. This gives the exceptional increase in velocity of 2.1 
meters for each 100 meters elevation. This condition is most naturally explained as 
a result of the retarding of the lower winds by friction against the ground. If it is 
assumed to arise from an undue excess of velocity immediately over the hill, then 
naturally the increase in velocity with greater altitude would be less than the normal 
until the kites rose entirely out of the influence of the hill into the normal conditions 
of the free air. However, the observations with kites are too few to settle the matter 
definitely. The results in Table XXII., added to the mean velocity at Blue Hill 
(7.2 meters per second), and the mean for Boston, are plotted in Plate V. Figure 3. 
The values above 400 meters are smoothed by taking the mean of each three suc- 
cessively. The individual records of the kite anemometer show wide variations. 
At times, the wind diminished with altitude, but at other times it increased so 
rapidly that the kites were unable to rise to great altitudes. On several occasions, 


96 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


when the kites passed from one current into another of a different direction and 
of a different temperature, the wind showed a sudden increase of velocity, and 
was stronger at the place of meeting between the two currents than above or below 


that plane. 


CHANGES IN DIRECTION OF THE CURRENTS. 


Differences in the direction of currents at different levels were shown by changes 
in the directions of the kites as they ascended. The kites usually shifted gradually 
toward the right as they ascended ; but shifting toward the left was not uncommon. 
However, the most prominent tendency in changes of direction was for the kites to 
come into currents from the west as the kites ascended. Regardless of the direction 
from which the kites started, they usually shifted around into currents from the west 
when they reached considerable altitudes. This was especially marked with winds 
from the south, even when there was a strong barometric gradient at the earth’s 
surface, causing winds from that direction. Such currents seem rarely to exceed a 
mile in depth. The diurnal current from the south, whose existence is shown by the 
diurnal rotation of the winds at Blue Hill, is very shallow. (See Discussion of the 
Cloud Observations, Annals of the Astronomical Observatory of Harvard College, 
Vol. XXX., Part IV. pp. 412-417.) When this current exists in the late afternoon, 
by the gradual shifting of the wind to the south, its upper limit rarely exceeds 200 
meters above Blue Hill. Above this, the winds probably join in the more general 
diurnal period shown by the clouds. The law of change in wind direction evidently 
is, that, as long as the winds into which the kites enter are controlled by the general 
barometric gradient prevailing at the earth’s surface, the deflection of the kites is 
toward the right as they ascend, provided that the velocity of the wind increases 
with increase of altitude, as is usual; but the kites are deflected toward the left 
when the wind velocity diminishes with increase of altitude. This effect is to be 
attributed to the earth’s axial rotation. When the kites have ascended to a con- 
siderable height, they generally pass out of the influence of the winds caused by 
the barometric gradient at the earth’s surface, and usually change their direction 
of flight more or less abruptly as they enter the current above. At times, how- 
ever, the change of direction with increase of altitude is gradual until currents are 
reached which are almost diametrically opposite to those below. This occurred 
on April 13, at 6 p.m, when the lowest kite was from the south-southwest, and 
successively higher kites were more from the west, while the highest kites were 
from the northwest. 


EXPLORATION OF THE AIR BY MEANS OF KITES. 97 


RESULTS FROM THE THERMOGRAPH RECORDS OF OcTOBER 8, 1896. 


A sample of the records of the kite meteorograph for August 26, 1896, is shown 
by a facsimile reproduction in Plate IV. Figure 29. 

In order to study the changes of temperature and humidity with varying altitude, 
the records of the kite meteorograph, after being tabulated and corrected, were 
plotted according to altitude for each flight. On the same sheet were plotted in 
the same way the changes in azimuth of the upper kites, observed from the ground. 
A facsimile of the meteorograph record for October 8, 1896, appeared in the 
Monthly Weather Review of the United States Weather Bureau for September, 
1896. A copy of the lines plotted as described above for that date is shown in 
Plate V. 

Figure 4 shows the change of temperature with varying altitude, beginning with 
the second ascent at 0:31 p.m. The altitudes above the Valley Station are used, and 
the temperature is plotted according to the altitude of each record. When the kites 
were ascending, dots indicate the recorded temperature, and are connected by a 
continuous line. When the kites were descending x’s indicate the recorded tem- 
perature, and are connected by a broken line. The same plan is followed in plotting 
the other elements. In the present case, the records during the ascent were obtained 
near the warmest part of the day; while the descent was made for the most part 
after sunset, the meteorograph reaching the ground shortly after 9 p.m. The two 
branches of the lines typify the temperature distribution vertically, as it is usually 
found in fair weather during the day and the night, respectively. In the con- 
tinuous line representing the day observations, the temperature falls uniformly, and 
at the adiabatic rate, to the cloud level. In the broken line representing the night 
observations, the lower part of the line is decidedly curved, showing a body of 
relatively cold air near the ground, due to radiation from the ground. There is a 
rise of temperature with increasing altitude up to a given height, and afterward 
a comparatively uniform fall as far as the cloud level, if clouds exist; but the rate 
of fall with increasing altitude shown by the upper part of the diagram is slower 
at night than during the day. The lines show that the diurnal changes of tem- 
perature are very small at great altitudes, compared with the changes near the 
earth’s surface. The lines connecting the temperatures, recorded at the same 
moment at the kites on the Hill and in the Valley, at or near the beginning of 
each hour, are given in Plate VI. Figures 1 and 2. They show the relation of the 
diurnal changes in the upper air to those in the lower air, in a way better than 
do the plotted lines in Plate V. The full lines connect observed values and the 


98 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


dotted lines are extrapolated. Records are available for the night at the Hill and the 
Valley stations only ; but after 10 a.m., records in the upper air are available from 
the kite thermograph for almost every hour up to 9 p.m. Figure 1 shows that 
after 10 a. M., at heights below 1,000 meters, the temperature of the air at all levels 
rose almost uniformly until 2 p.m. This rise may be explained by the ascent of 
the heated air from the earth’s surface. The air, heated at the ground, in rising is 
cooled by expansion at the adiabatic rate, namely, about 1°C., or 1°.8 F., for each 
100 meters of ascent in unsaturated air. Air descending to take the place of the 
rising body is heated by compression at the same rate; so that the entire atmos- 
phere between the upper limits of the ascending columns, or when clouds exist 
between the base of the clouds and the ground, is found to cool with ascent at 
the adiabatic rate of unsaturated air, as shown by the lines after 10 a. m. for October 8 
in Figure 1. 

Now, if air, heated at the ground and cooling by ascent at the adiabatic rate of 
unsaturated air, rises, say to 1,000 meters, its temperature will be 18°F. lower than 
when it left the ground. If an hour later the temperature has risen 2°F..at the 
ground, the air rising from the ground to 1,000 meters and cooling 18° F., as before, 
will be 2° F. warmer than was the air at the same level an hour previous. The same 
is true for any intermediate level; so that the entire atmosphere through which the 
ascending currents pass will be warmed at the same rate as the air near the ground. 
It is to be noted, however, that this does not occur until the ascending currents (and 
the consequent adiabatic rate of fall of temperature) are established ; and it extends 
only to the tops of the ascending currents, which probably reach successively higher 
and higher altitudes as the day advances. It follows that the highest levels reached 
by the ascending currents partake of the progressive rise of temperature only for 
a short time preceding the warmest part of the day. Hence they change their 
temperatures but little. The tops of these ascending currents are well outlined on 
fair days by the tops of the cumulus clouds; and these tops, which are usually found 
below 2,000 meters, show the upper limit of the diurnal heating which may arise from 
this cause. The full lines for 6 a. mM. and 7 a.m. in Figure 1 show that, at these 
hours on October 8, the temperature was lower in the Valley than on the Hill. 
Between 7 A.M. and 8 A.M., there was a rapid rise in temperature at the Valley 
Station, and the adiabatic rate, indicating the formation of ascending currents, was 
established between the upper and the lower station. The dotted lines, extending 
the full curves, are intended to show what was the most probable distribution of 
temperature above the Hill during the early morning. Soon after 2 Pp. mM. the tem- 
perature at the ground and at the kites ceased to rise, and in Figure 2 are drawn 


EXPLORATION OF THE AIR BY MEANS OF KITES. 99 


lines connecting the temperatures recorded near the beginnings of the afternoon and 
the evening hours at the kites, on the Hill, and at the Valley Station. These lines 
show that the adiabatic rate of change of temperature between the ground and the 
kites was departed from immediately after the warmest part of the day; and that 
the difference in temperature between the kites and the ground became rapidly less, 
on account of the quick fall of temperature at the ground, while the temperature at 
the higher levels fell very slightly. The fact that the adiabatic rate of fall of tem- 
perature between the ground and the kites ceased about 3 Pp. m. (the records in each 
case being used only when the kites were below the base of the clouds), indicates 
- that the ascending currents from the ground ceased about this time. Yet the clouds 
formed by these ascending currents persisted until after 6 Pp. m., but were almost 
entirely gone by 7 p.m. This delay in clearing may be explained partly by the 
delay required for the ascending currents to reach the cloud level. But since the 
temperature aloft must continue to rise until the warmest air which leaves the 
ground arrives, and since the maximum temperature near the cloud level was reached 
about 3 p.m., or shortly after, the delay in the cessation of cloud formation on this 
account could not have been long. It seems evident that the clouds existed for two 
or three hours after the cessation of the ascending currents by which they were 
formed. The successive measurements of the altitudes of the cloud bases, by kites 
entering or leaving the clouds, show that the bases of the clonds rose rapidly until 
the warmest part of the day, and then sank slowly. This is shown in the following 
observations, in which the first height is taken from the humidity curve, the kites 
not being seen actually to enter the cloud. 


Time... . . 11:184a 1:58P 2:05P 2:39P 3:01P 3:34P 3:56P 4:34P 4:57P 5:23 P 
Altitude in meters. 713 1178 §=61224 1341 1454 1408 13860 1344 1330 1370 


This result agrees with the average of measurements made by theodolites on a 
large number of days in showing an increase in height of the bases of the cumulus 
until the warmest part of the day, and then a decrease. 

It is probable that, after the ascending currents cease with the warmest part of 
the day, the cumulus subside slowly under the influence of gravity, and at the 
same time gradually dissipate. Cumulus, however, do not always cease to form 
after the temperature at the ground begins to fall in the afternoon. In some 
cases I have observed fresh cumulus forming after sunset, but such cases preceded 
cooler weather; and it is probable that the adiabatic rate persisted in the lower 
air on account of the rapid inflow of cooler air aloft, as explained below in the 
discussion of the vertical distribution of temperature in cold waves. 


100 BLUE HILL METEOROLOGICAL OBSERVATIONS, 


The vertical distribution of temperature on October 8 is further illustrated in 
Plate VI. by isothermohyps (equal temperature heights), a name suggested by Pro- 
fessor W. M. Davis. These curves are drawn by reading, from the lines in Plate VI. 
Figures 1 and 2, the altitude at which each temperature ending in 0° or 5° F. was 
found at each hour, and by plotting the altitudes with dots. These are then con- 
nected by continuous curves showing the changes in altitude of the given temperature 
during the course of the day. The chart shows near the ground a complex set of 
curves caused by the inversion of temperature with increase of altitude at night. 
But above 400 meters there is probably a simple diurnal curve with a single maxi- 
mum and minimum, the range of which diminishes with increasing altitude, and 
probably above 2,000 meters reaches, or approximates, zero. 

The conditions found on October 8 below the cloud level are typical of the 
conditions found on all fair days with cumulus clouds. The conditions above the 
cloud level on October 8 will be considered when discussing the temperature curve 
designated Type 4. However, the records indicate that a diurnal change in tem- 
perature exists at a greater altitude on days with cumulus clouds than on other 
days, when the ascending currents from the ground are weak or are prevented by 


some cause from reaching a great altitude. 


DiurNAL CHANGES OF TEMPERATURE AT DIFFERENT ALTITUDES. 


The isothermals drawn from the records of the kite meteorograph, illustrated in 
Plate VI., indicate that the maximum temperature at moderate altitudes in the free 
air occurs in the early afternoon, and the minimum occurs during the night. The 
same is shown by observations on mountain peaks. In other words, a curve repre- 
senting the diurnal changes in the air at some distance above the ground is probably 
similar to one representing the changes near the ground, except that the amplitude 
is less. If this is true, then the diurnal rate of fall for any given time at any 
two levels will be proportional to the daily ranges of temperature at the two 
levels. Hence, if the average rate of hourly fall during the afternoon is known 
from simultaneous observations at any two levels, and the daily range is known 
for either level, then the daily range at the other level can be found by multi- 
plying the known range by the ratio between the falls found at the two levels. 
It is impossible in practice to keep a kite at exactly the same level for 24 hours; 
hence the daily ranges for the different levels must be found by comparing the 
rates of rise or fall of temperature for given times with the rates found from 
records near the ground made simultaneously with those above. The records of 
the kite meteorograph were made chiefly during the afternoon. In order to get 


EXPLORATION OF THE AIR BY MEANS OF KITES. 101 


the ratio of fall for the same intervals at altitudes of 500 meters and at the 
ground, the records made by the kite meteorograph near 500 meters, when the 
kites were ascending, are discussed below; also those made near the same level 
when the kites were descending. Cases are taken only when the meteorograph 
was approximately stationary long enough to take the true air temperature. Dif- 
ferences of level are corrected by reducing the temperature at the level farthest 
from 500 meters to that of the level of the record made nearest 500 meters. Thus, 
on August 26, 1895, records were made at 449 meters and 546 meters when the 
kites were ascending, and at 501 meters when the kites were descending. ‘The fall 


TABLE XXIII. 


SYNCHRONOUS CHANGES OF TEMPERATURE NEAR 500 METERS, ON BLUE HILL AND 
AT THE VALLEY STATION. 


Altitude Observed Change in Change per Hour in 
Time. of Kite Temperature Temperature 
Date. above 
P.M. 
Valley. 


at Kite. on Hill. in Valley. at Kite. on Hill, | in Valley. 


1895. hrs. and min. | meters. or: oF, oF, oF. oF. oF, 
Aug. 3:46-5:37 | 501 | —2.0 6.7 O00 me we —3.6 — Sal) 
Aug. 4:55-5:55 | 521 | —3.0 3.0 Cay BAN — 3.0 —4.9 
Dee. 2:56-4:14 | 473 | —0.38 1.0 LS 1 530.2 —0.8 =1.0 

1896. 
April 4:26-6:24 | 506 | -1.9 | — 35 | — 3.7 | —1.0 aot Lae a A 
June 5:07 —d:150 1 Oote teen fee tO | = 0.2 — 0.9 =D 
June 4:10-9:55 | 527 | —4.9 | —10.9 | —13.1 | —0.8 Sy, —2.3 
April 4:25-5:34 | 483 | —5.2 | — 2.7 | — 18 | —4.5 ee ea A) 
April 3:54-6:35 | 528 , 9.6 atl Nf = G — 5.6 
April : 3:07 — 5:05 | 501 ; 2.9 — 0.6 =—1.5 — 0.4 
May 3:04-5:17 | 558 Ce P18 = 008 =a 
May 2:36-4:43 | 524 4.7 +2.0 — aah 
June 2] 4:20-6:23 | 480 : 2.1 ri —().9 = 1.0 > hz 
July 2:56-4:10 | 520 0.8 | —0.2 a 
July 5:02-5:18 | 490 2.4 ; = 0.5 = OL5 — 0.4 
July 1:43-6:15 | 510 2. ; —0.6 a 
Aug. 4:13-9:42 | 511 ). Reh hi ero.0 
Sept. 4:34-6:22 | 482 ; +0.8 : Zk 
Sept. 1:01-4:09 | 520 1 | +03 0 | -16 
Sept. 3:39-10:05 | 504 ; 8. ley’ baci Es, 
Sept. 3:26-5:56 | 500 ; : ; == ()0) — 4.5 
Oct. 0:31-8:50 | 551 5 — 0.3 —1.7 
Noy. 2:42-5:04 | 473 ‘ : —0.9 “ —2:4 
Dec. 2:28 —3:22 | 457 : + 2.2 —1.6 

1897. 
Jan. 21] 0:01-5:32 | 524 . ; : 1.5 — 0.5 
Feb. 10 | 3:43-6:36 | 610 : ; PUnih = 0.8 


Means 512 — 0.42 


102 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


of temperature between 449 and 546 meters was 2°.8 F., or 0°.029 for each meter 
of ascent. Consequently, to correct for the difference in level of 52 meters between 
501 and 449 meters, it is necessary to subtract 1°.5 from the temperature recorded 
at the altitude of 449 meters. Then in the 111 minutes elapsing between the times 
when the kites passed these altitudes in ascending and descending the fall of 
temperature was 2°.0. The fall of temperature during the same interval on Blue 
Hill was 6°.7 and at the Valley Station 5°.6; the rate of fall per hour at the 
three places being respectively 1°.0, 3°.6, and 3°.0 F. In this way, Table XXIII. 
is constructed to show the synchronous changes of temperature aloft and at the 
ground. 

The mean rates of hourly change, given at the foot of Table XXIII., show that 
the rate of change at the Valley Station is 4.90 times as great as that at the kites; the 
change on the Hill is 3.82 times as great as that at the kites; and the change at the 
Valley is 1.27 as great as that on the Hill. Now, if the supposition is correct that 
these ratios are in proportion to the total daily ranges of temperature at the respect- 
ive stations, then the total mean range at the Valley divided by 1.27 should give 
the range on the Hill, and divided by 4.90 should give the mean daily range at the 
kites. The mean daily range at the Valley Station, found from the observations for 


TABLE XXIV. 


SYNCHRONOUS CHANGES OF TEMPERATURE AND HUMIDITY NEAR 1,000 METERS, ON BLUE HILL 
AND AT THE VALLEY STATION. 


Observed Change per 
Change in Hour in 
Humidity Humidity 


Altitude Observed Change in Change per Hour in 
of Kite Temperature Temperature 
above 
Valley. 


Wee as oe a  N ! 
at Kite. | on Hill. |in Valley.| at Kite. | on Hill. |in Valley. Jat Kite.| on Hill.| at Kite. | on Hill. 


1896. hrs, and min. | meters. oF, c oF, oF, oF, - | perct. | perct.| per ct. | per ct. 
April 18 | 4:48-6:20} 899 | +1.0 : 10.8; +0.6 | —4.0 
May 8:04-4:15 | 1083 | +4.2 ’ 2.0 — 5} + 2) — 
June 1:56-4:00 | 1006 | +0.4 ie 2.6} +0.2 | —1.9 any 
| June | 3:24-4:45 | 1000 | +0.2 ; OVt ae Os eae 
| June 22) 5:32-7:43 | 1024 | —0.2 3 4.6) —OL) | —2:5 
i July 22) 0:42-4:29] 1160 | —1.4 2. 1.38} —0.4 | —0.7 
July 23 | 3:56-6:08 | 1025 | —1.2 3.8} —0.5 
Aug. 22 | 8:28-5:31] 1003 | —0.1 ; 0.6) 0.0 | —0.9 
Aug. 4:48-9:13 | 1041 | —1.0 Oh — 16-0 = 2d 
¥ Oct. 0:59-8:24 | 1098 | —1.0 .6 | —14.3; —0.1 | —0.9 
| Nov. 3:02-4:32 | 1004 | —0.7 8|— 3.0| —-0.0 |—1.2 
1897. 
Jan. 8:16-4:27 | 1031 | +0.6 2:0)| =~ 2.6) + Oo eS Ieh 
Feb. 10) 4:20-6:16] 990 0.0 10) = 5.5 OOM 2a 


Means 1024 — 0.03 | —1.78 


EXPLORATION OF THE AIR BY MEANS OF KITES. 103 


eight years at that place, is 20°8 F.; this, divided by 1.27, gives 16°.4, and, divided 
by 4.90, gives 4°.2. The observed range at the summit of the Hill, from observations 
for eleven years, is 16°.7 F. Since this agrees very closely with the range computed 
above (16°.4), it seems fair to conclude that 4°.2 is also a close approximation to the 
true range at 500 meters. If the observed range at the summit of the Hill (16°.7) is 
divided by 3.82 (the ratio between the mean hourly changes found at the kites and 
on the Hill), then 4°.4 is obtained for the range at 500 meters. The mean of the two 
methods gives the range as 4°.3 F. 

For altitudes of about 1,000 meters, Table XXIV. is constructed in the same 
manner as was Table XXIII. for altitudes of about 500 meters; except that changes 
of relative humidity are also included in Table XXIV. 

These results, treated in the same way as the means in Table XXIII., show that 
the daily range of temperature at 1,000 meters is 0°.3. The result is the same, 
whether the ratio of change is taken from the Valley or the Hill Station. 

These results show also that the diurnal range of temperature diminishes rapidly 
with increasing altitude in the free air, and almost disappears, on the average, at 
a height of 1,000 meters. Probably, however, it occasionally extends to altitudes of 
2,000 meters. The average diurnal ranges (determined by direct observations and 
computed from the kite meteorograph records at different altitudes, counting from 
the level of the Valley Station, which is itself 15 meters above sea level) are as 


follows :— 
Valley Station. Base Station. Summit Station. Kite. Kite. 
Diurnal Range in deg. Fahr. —20°.8 Les 1637 4°.3 0°.3 
Altitude in meters 0 49 180 500 1000 


The Base Station is at the foot of the northern slope of Blue Hill; beyond, the 
land slopes more gently to the Neponset River, near the banks of which is the Valley 
Station. With these ranges may perhaps be compared the range of 10°.1 F., obtained 
from observations for five years on the Eiffel Tower at an altitude of 500 meters, 
since this range no doubt approximates the true diurnal range in the free air at that 
height, and the range at the foot of the tower is approximately the same as the range 
at the base of Blue Hill. 

These results are plotted for their respective heights in Plate V. Figure 1. The 
points are connected by a continuous line, and, besides, a smoothed curve is drawn 
through them. The smoothed curve passes approximately through every one of the 
observed and the computed ranges, except the one at the summit of Blue Hill, which 
is too great. This evidently is because insolation and radiation, acting through the 
soil of the hill, heat and cool the air to a greater extent than the free air is heated 


104 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


and cooled at the same altitude. This must be true at every mountain station. The 
smoothed curve passes also very slightly to the left of the result for the Eiffel Tower, 
indicating that the range there is about 1° F. greater than the true-range, on account 
of the heating and cooling of the tower. If the diurnal range for the altitude of the 
top of Blue Hill is taken from the smoothed curve in Figure 1, it is 12°.4 F., which 
is 4°.3 lower than the observed range. 


DiurNAL CHANGES OF RELATIVE Humipity AT DIFFERENT ALTITUDES. 


In order to study the diurnal changes of relative humidity at different altitudes, 
Table XXV. is prepared from the records of humidity, in the same manner as Table 
XXIII. is made from the records of temperature. 


TABLE XXV. 


SYNCHRONOUS CHANGES OF RELATIVE HUMIDITY NEAR 6500 METERS, AND ON BLUE HILL. 


Time. ase Observed Change | Change per Hour 
Date. ; 

P.M. above 
Valley. | at Kite. | on Hill. | at Kite. | on Hill. 


1896. hrs. and min. | meters. . ret. | perct. per ct. 
April 11 | 4:25-5:34 | 483 2» +9 +2 
April 13 | 8:54-6:35 | 528 3 | +1 tt 
April 24 | 8:07-5:05 | 501 a +3 
May 7 | 3:04-5:17 | 558 Vi (ek +3 
May 9 | 2:36-4:43 | 524 —3 +1 
June 4:20-6:23 | 480 —3 came 
July 2:56-4:10 | 520 +6 
July 1:43-6:15 | 510 al! 
Aug. 4:13-9:42 | 511 +6 
Sept. 4:34-6:22 | 482 si 
Sept. 1:01-4:09 | 522 —1 
Sept. 8:26-5:56 | 500 +6 
Oct. 0:31-8:50 | 551 —1 

1897. 
Jan. 2 | 0:01-5:32 | 524 —4 
Feb. 3:43-6:36 | 610 +1 

Means 518 + 0.6 
Diurnal Range 3.5 


ear 
oo 


2 
0 
3 
6 
8 
6 


ap, 
—_ 
Oomcd bt & &w 


=f 
bs 
oe 


In computing the diurnal range, given at the foot of this table, the data are 
treated in the same way as described in connection with Table XXII. No records of 
humidity were obtained at the Valley Station. The synchronous changes in relative 
humidity near 1,000 meters and on the summit of the Hill are given in Table XXIV., 


in which the means show reversed signs. In other words, as night approaches, the 


EXPLORATION OF THE AIR BY MEANS OF KITES. 105 


humidity at the altitude of 1,000 meters diminishes, while at the earth’s surface it 
increases. This agrees with the evidence furnished by the cumulus clouds which form 
during the day between 1,000 and 2,000 meters altitude, and which disappear at 
night, thus visibly indicating an increase of humidity by day, and a decrease by night. 
If the form of the humidity curve at a height of 1,000 meters is assumed to be the 
reverse of that found at the ground, then the results got from the kite meteorograph 
show a diurnal range of 14.7 per cent at 1,000 meters, with the minimum humidity 
at the coldest, and the maximum humidity at the warmest part of the day. These 
mean daily ranges for different altitudes are plotted in Plate V. Figure 2. The part 
of the plotted line at the left of the zero line shows the range at different altitudes, 
with the minimum humidity near the warmest time of day; while the part at the 
right of the zero shows the ranges at different altitudes, with the minimum humidity 
at the coldest time of day. 


Types oF TEMPERATURE CHANGE WITH ALTITUDE. 


When the records of temperature and humidity, made aloft by the kite meteoro- 
graph and at the stations near the ground, are plotted in relation to altitude, and 
lines are drawn connecting the observed values, the resulting lines are found to be 
distinetly divisible into a few types. Hxamples of each of these types. plotted 
directly from the records on selected days, are shown in Plate VII. 

Type 1, Plate VII.,is plotted from the records of temperature on July 25, 1896. 
It represents the decrease of temperature on most fair days, from the ground to 
altitudes of a mile or more, when no clouds are met. On August 26 the ascent 
was made during the late afternoon between 4 and 6 o'clock, and the meteorograph, 
after remaining near the highest point for about two hours, was drawn down in the 
night between 8 and 10 o’clock. The continuous line, plotted from the records of 
the ascent, represents the day conditions, and the broken line, plotted from the 
records of the descent, represents the night conditions. This curve differs from the 
normal of this type only in the fact that the broken curve shows a higher tem- 
perature during the night than during the day, at altitudes above 1,100 meters. 
Observations, as previously shown (p. 103), indicate that no diurnal change exists 
at this altitude. However, with the approach of warmer or colder weather, the 
temperature continues steadily to rise or to fall during either night or day. This 
curve shows that with increasing altitude the temperature falls uniformly, and 
approximately at the adiabatic rate, during the day. The fall is strictly at the 
adiabatic rate, or about 1°.8 F. in unsaturated air, for each 100 meters of ascent, 


during the morning and early afternoon, as shown on October 8; but it begins 


106 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


to depart from this rate in the late afternoon. The fall of temperature with 
increasing altitude in the night is much slower than in the day. In fact, from 
the earth’s surface to an altitude of a few hundred meters, there is a rise of 
temperature with height, and the air at altitudes of from 300 to 500 meters is 
considerably warmer than at the ground. 

When clouds are met during the flight, the temperature curve assumes the form 
of Type 2. This curve is plotted from the records of July 20, 1896, when both 
ascent and descent were in the daytime. The continuous curve is plotted from the 
records of the ascent; the broken curve, from the records of the descent. In the 
ascent, the base of the cumulus clouds was entered at a height of 866 meters 
above the Valley Station. In the descent, the instrument came out of the base 
of the cumulus at a height of 1,022 meters. The humidity record shows that the 
meteorograph passed out of the top of the cloud in the ascent at a height of about 
1,100 meters, and re-entered the top of the cloud in the descent at a height of 
about 1,400 meters. The plotted line shows that the temperature fell, at the adia- 
batie rate in unsaturated air, till the level of the base of the cloud was reached. 
It fell at a slower rate while the instrument was in the cloud, the rate probably 
being that computed by physicists as the adiabatic rate for air in which conden- 
sation is taking place; but this could not be determined with accuracy, because 
the instrument was successively entering and leaving the sides of different clouds 
drifting across it. Above the clouds, the fall of temperature was very slow; but 
this condition may have been abnormal. At night, the curve representing Type 2 
has the same form near the ground as Type 1. 

Type 3, Plate VII., is drawn from the records of December 21, 1895. It is a type 
of curve which persists throughout the day and night; and it resembles the night 
form of Type 1. The ascent was made between 2:13 and 3:16 p.m.; and from 
the records the continuous line is plotted. The descent was made between 3:30 
and 4:47 p. m., the instrument thus reaching the ground about thirty minutes after 
sunset. This descent gave the records from which the broken line is plotted. The 
records from the Blue Hill Base Station (49 meters above the Valley) are also in- 
cluded in the plotted lines. The lines show that the temperature rose very rapidly 
for a short distance above the ground, and then fell, as the height increased, at a 
rate somewhat less than the adiabatic rate. The rate of fall of temperature shown 
by the upper part of the curve obtained during the descent is slightly slower than 
that in the curve obtained during the ascent; and the rise of temperature near the 
ground with increasing altitude is much more marked after sunset than during the 
daytime. At 3:30 p.M., when the meteorograph was at the highest altitude (614 


EXPLORATION OF THE AIR BY MEANS OF KITES. 107 


meters), the temperature was slightly lower at the Valley Station than at the kites; 
and the difference probably increased during the night. In the present case, which 
is probably characteristic, the highest temperature was found between 100 and 200 
meters above the Valley Station; but on other occasions with this type of curve, as 
on November 17, 1895, the highest temperature was at altitudes of 400 meters, or 
slightly higher. 

Type 4, Plate VII., is plotted from the records of the ascent on September 29, 
1896. No records were obtained during the descent. This type is also repre- 
sented by the temperature curves obtained on October 8, 1896, shown in Plate V., 
in which both the day and the night conditions are represented. This form of 
curve is produced by a warmer current overflowing colder air, —a condition 
which is very commonly found at low altitudes in the atmosphere, and probably 
exists usually at some altitude, great or small. It might perhaps be called the 
normal type of curve. This type may be found when colder air is pushing from 
the east or north near the ground beneath an opposing warmer current; but in a 
large majority of cases, when found below altitudes of 2,000 meters, it is caused 
by the approach of a warm wave, the upper air of which, partaking of the rapid 
movements of the upper currents from the west, advances faster than the lower 
part of the warm wave, and overflows the colder air in front. Hence this type 
may be called the warm wave type. A knowledge of its existence enables one to 
forecast the arrival of a warm wave, with a high degree of certainty, from eight 
to twenty-four hours in advance. | 

The characteristics of this type of curve are as follows: during the day a de- 
crease of temperature, at the adiabatic rate, from the ground to an altitude of 
several hundred meters; then a sudden rise of temperature in the next 100 meters 
or 200 meters of ascent; and, afterward, a slow fall of temperature, with increas- 
ing altitude usually at a rate much less than the adiabatic rate. The rise of 
temperature in passing from the cold to the warm current may be as much as 
25° to 30° F., as on January 2, 1897. The sky is sometimes clear when these con- 
ditions exist, as on April 13, April 27, May 9, August 1, and December 12, 1896; 
but usually clouds are found near the meeting of the warm and the cold current. 
Sometimes the clouds are in the warm current, immediately above the plane of 
meeting of the two currents; at other times, the clouds are in the cold current, 
immediately below the plane of meeting; and occasionally they seem to exist 
between the two currents. Clouds immediately above the plane of meeting of the 
two currents were found on February 13 and September 29, 1896; clouds immedi- 
ately below the plane of meeting were found on October 8, November 18, 1896, 


108 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


and January 2, 1897; clouds exactly between the two currents were found on 
November 23, December 9, 1895, and September 17, 1896. 

At first, I was inclined to attribute these cloud formations to a mixing of the air in 
the plane between the two currents of different temperature ; but a careful study shows 
that this cannot be the cause in many, if not most, of the cases. In the two cases 
where the clouds were above the plane of meeting of the warm and the cold current, 
the cloud sheets were very dense. On February 13, precipitation occurred at the 
time of the ascent, and continued during the day. On September 29, the hygrograph 
showed that the cloud was more than 700 meters thick, because the air continued to 
be saturated from the time when the hygrograph entered the cloud at 900 meters to 
1,600 meters, — the highest point reached. Hence it is impossible to attribute the 
cloud formation to cooling by mixture with the lower current, because the air at the 
highest point reached was several degrees cooler than the top of the cool current 
beneath. Therefore it could not possibly have been cooled to the dew-point by 
admixture. The explanation of the cloud formation probably is that the plane of 
meeting between the currents was a slanting one, the cooler current being wedge- 
shaped; and that the warmer air, in moving upward along this slope, was cooled to 
the point of saturation by expansion. The cooler currents are sometimes wedge- 
shaped, as is shown by frequent observations from the top of Blue Hill of cooler 
currents, filled with fog, advancing against or retreating before warm southerly 
currents. In such a case, the southern edge of the cooler current is very thin, and 
does not extend higher than the tree tops; farther north, however, it grows gradually 
thicker, until the tops of the highest hills are hidden by the fog. Several cases of this 
kind are described in the Discussion of the Cloud Observations. (Harvard Annals, 
Vol. XXX. Part IV.) In such cases, the fog is probably produced by streaks of the 
warmer air drawn down into the cooler air by the invisible undulations, like ocean 
waves, between the two currents. 

In the case of clouds beneath the plane of meeting of the currents, there were 
evidently several causes for cloud formation: ascending currents; mixture; conduc- 
tion; and possibly other causes. The two following cases, namely, October 8, 1896, 
and January 2, 1897, illustrate these conditions. 

On October 8, 1896, scattered fracto-cumulus began to form about 9 A. M. in the 
currents ascending from the ground, as on ordinary fair-weather days. When the 
temperature near the ground rose, the bases and the tops of these clouds were formed 
at higher and higher altitudes until about noon, when the tops of the ascending 
currents reached the base of the warmer stratum of air. Further ascent was stopped 


EXPLORATION OF THE AIR BY MEANS OF KITES. 109 


as if by a wall, because even the warmest air in the colder current was denser and 
heavier than the air of the warmer upper current. The result was, that, when the 
tops of the clouds reached the plane of meeting between the currents, they began to 
spread out, and to join one another; so that by noon, and during the entire afternoon, 
the sky was covered with strato-cumulus, through the breaks in which the kites could 
be seen at intervals. The bases of these clouds, however, continued to rise until the 
warmest part of the day, because the diminishing relative humidity, as the heat 
increases, makes it necessary for the air columns to rise to greater altitudes before 
condensation begins. ‘Toward evening, after the ascending currents had ceased, these 
clouds cleared away, as do ordinary cumulus. 

On January 2, 1897, several causes appeared to be active in the cloud furmation 
and its subsequent changes. The sky was covered with a dense uniform sheet of 
stratus until noon. The kite meteorograph passed through this stratus at noon. The 
record shows that the sheet was then 142 meters thick, and formed the top of a cold 
stratum of air. Immediately above this cold stratum, another stratum of air more 
than 25° F. warmer was found. In the ascent, the temperature decreased with alti- 
tude, at the adiabatic rate in unsaturated air, up to the cloud level; and there were 
evidences of ascending currents, because the clouds immediately afterward broke into 
strato-cumulus, which grew gradually thinner and almost entirely disappeared between 
land2p.m. Evidently the causes of these phenomena are as follows. As soon as 
the ground became warmed by insolation (which is felt to some extent even through 
the densest clouds), ascending currents were formed. These compelled the simul- 
taneous formation of descending currents, from the tops of which cloud matter was 
drawn downward and rapidly evaporated by warming in descent; at the same time, 
the clouds grew thicker at the top of the ascending columns by cooling in ascent, | 
thus breaking the stratus into strato-cumulus. While the diurnal heating at the 
ground increased, the relative humidity, in consequence, diminished; the ascending 
air rose to higher levels before vapor condensation began, and the clouds grew thinner, 
because the tops of the ascending currents were limited to the lowest level of the 
warmer upper current. Finally, with increasing heat at the ground and with dimin- 
ished humidity, the ascending currents rose to the level of the warmer current before 
condensation by expansion could occur; consequently, all cloud formation ceased in 
the lower level, leaving the sky clear, except for a few cirrus at a very great height. 
The sky remained clear during the warmest part of the day, but toward evening 
fracto-stratus began to form. By 7 p. m., the sky was again covered with a uniform 
sheet of stratus, which continued during the night. The descent of the kite meteoro- 
graph between 5 and 6 p. m., about an hour after sunset, showed that the adiabatic rate 


110 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


of change of temperature with change of altitude, in the lower air, had disappeared ; 
and the colder air stratum had nearly the same temperature from top to bottom. 
The question then is, What was the origin of the stratus cloud (then about 170 
meters thick) which was again forming at the top of the cold stratum ? 

This stratus could not have been caused by an admixture in equal proportions 
of the warm and the cold current; because, first, the temperature of the cloud 
stratum was not a mean between the two currents; and, second, the relative 
humidity of the upper current (49 per cent) was too low for condensation to 
take place by complete admixture of the two currents. But the dew-point, or 
temperature of condensation in the warm current, was 37°, while the temperature 
at the top of the cold current was 34°. Hence it is evident that, if a thin layer 
of the warm current could have been cooled to the temperature of the lower 
current by the conduction of its heat to the lower air, then condensation of its 
moisture into a cloud might have occurred. However, this does not seem to satisfy 
the conditions, because the reverse of this was apparently taking place. For the 
base of the warmer current was found about 100 meters lower when the kite 
meteorograph descended than when it ascended; indicating that the top of the 
colder current was being warmed. The most satisfactory explanation of these 
conditions is that occasional thin sheets, or streaks, of the upper air were drawn 
down into the lower air by the tossing to and fro of the air in the wave-like 
agitation which was evidently in progress. The agitation was doubtless caused 
by friction between the two currents. ‘These thin streaks may be cooled virtually 
to the same temperature as the lower air; so that the excess of moisture existing 
between the upper air dew-point and the lower air temperature would be condensed 
as cloud. It is analogous to the condensation of the breath emitted from the lungs 
in a cold morning. Such breath is cooled to the temperature of the air, and forms 
an evanescent cloud. It is true that enough of these streaks cooling to form a 
cloud sheet must, to a certain extent, raise the temperature of the lower air. This 
apparently was taking place on January 2, 1897, because the top of the colder air 
during the descent of the kites was found to be warmer than during their ascent. 
In whatever way the cloud stratum was formed in the night, further condensation 
must have been aided by radiation from the cloud. It should be mentioned in 
connection with this, that much the strongest wind encountered on January 2 (as 
proved by the pull of the kites) was in a thin stratum between the warm and the 
cold current. Both above and below this level the winds were weaker, and at the 
highest point reached they were barely strong enough to support the kites. 
The strong wind was also from a more westerly direction than was the wind above 


EXPLORATION OF THE AIR BY MEANS OF KITES. tae 


or below it. The clouds found between a warm and a cold stratum, as on Novem- 
ber 23 and December 9, 1895, are in all probability clouds of mixture. 

The days when this type of vertical distribution of temperature, was found without 
cloud formation were evidently days when the humidity of both air strata was too 
low for clouds to form, either in the ascending currents from the ground, or by 
mixture between the currents. One of these days, April 15, 1896, furnishes an 
interesting example of the breaking up of this vertical distribution of temperature. 
On this day, between 9 and 10 a. m., during the ascent (see Table XVII), a much 
higher temperature than that at the ground was found at an altitude of about 500 
meters. On the descent of the kite meteorograph, about three hours later, between 
noon and | p. m., this abrupt rise of temperature at a height of about 500 meters 
had disappeared, and the temperature was found to decrease from the ground to the 
highest point reached by the kites. Between 3 and 4 r.m., fracto-cumulus began 
to form at a considerable altitude, and soon covered a large part of the sky. The 
probable explanation is that the intense insolation near the ground, uninterrupted 
by clouds, rapidly raised the temperature of the ground and the adjacent air; so 
that the heated air, carried up by the ascending currents, had by noon become 
slightly warmer than the air at 500 meters. Hence the ascending currents were 
able to penetrate the upper stratum. Up to that time the ascending current had 
been stopped by the warmer current above; no cloud formation was possible, because 
the lower air was relatively dry, and the altitude of the warm upper current was 
too low for condensation to take place from cooling by expansion in the lower 
ascending currents. But after the ascending currents had once penetrated the 
upper stratum, the air there was caught in the descending currents which brought 
to the ground the increasing warmth imported by the warm wave coming from the 
west. This aided the insolation in increasing the temperature at the ground, so 
that the diurnal maximum temperature was prolonged until about 4 p.m. It is 
usually found two hours earlier at Blue Hill. It seems probable that this vertical 
distribution of temperature (shown by Type 4) is usually broken up in this way. 
That this is not the only method, however, seems to be proved by the sudden 
rises of temperature which sometimes occur in the night. In forecasting the daily 
weather, the value of a knowledge of this form of temperature distribution seems 
apparent; because on it depend the answers to the questions whether clouds of 
certain kinds can be formed; what changes existing clouds can undergo; what 
shall be the distribution of the diurnal cloudiness ; whether cumulus clouds will be 
flattened, or whether they will form towering clouds; and hence whether showers 
are possible or not. 


112 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


The reverse of Type 4, that is, a sudden fall of temperature at a given altitude 
due to a colder current overlying a warmer one, is probably impossible, because 
the colder air, on account of its increased weight, would immediately begin to sink, 
and the warmer air to rise. This would cause the fall of temperature to take the 
adiabatic rate from the ground to the top of the colder current. This is probably 
the process of origin of Type 5, Plate VII., which is characteristic of cold waves. The 
example given is plotted from the records in the cold wave of January 19, 1897. 
The continuous curve is plotted from the records of the ascent, and the broken 
curve from the records of the descent. The parts of the curves oscillate somewhat 
from side to side; but the mean result shows a fall of temperature with increase 
of altitude, at the adiabatic rate of unsaturated air, from about 300 meters to the 
hi 


more rapid than the adiabatic rate. This is the especial characteristic of the 


ghest point reached. Below 300 meters, the rate of decrease of temperature is 
cold wave type of curve during the day hours. The excessive rate of decrease of 
temperature below 500 meters probably results from two causes: first, on account 
of the freer movements of the upper currents, colder air is moving in aloft more 
rapidly than at the ground, so that air rising from the ground is not only cooled 
by expansion, but also by contact with colder air aloft; second, the air coming in 
contact with the ground is heated more rapidly than usual. This latter condition 
results not only because the sun shining through the dry, cloudless, dust-free air 
of the cold wave causes greater heating of the ground by insolation than normal ; 
but also because the ground is warmer than the air from the fact that the air of the 
cold wave is colder than the normal temperature of the latitude in which it is found. 
The night form of Type 5, notwithstanding the excessive radiation from the ground 
through the dry air, shows a rapid decrease of temperature with increase of altitude 
from the ground upward. In this way it differs decidedly from Type 1 and Type 2. 
This fall of temperature with increase of altitude is not so rapid near the ground 
in the night as in the day; but it is apparently at the adiabatic rate in dry air 
(1°.8 F. in 100 meters). If for any night on which the temperature fell rapidly 
as a result of an approaching cold wave the thermograph records at the Blue Hill 
Valley Station and at the summit of Blue Hill are corrected for instrumental errors, 
and are placed one over the other, the curves will be parallel, and the temperatures 
at the summit will be found lower than at the Valley Station by almost exactly 
3° F., which is the adiabatic rate of decrease between the two stations. At least, 
this condition was found in an examination of the records during a number of 
well marked cold waves. Hence, with such conditions, it seems possible for cumulus 


clouds to exist all night; and even for thunder-showers to occur, if the lower air 


EXPLORATION OF THE AIR BY MEANS OF KITES. 113 


is damp enough. This sometimes happens during the night at the beginning of a 
cold wave. In fact, the formation of the cold wave type of curve is probably the 
cause at any time of day of severe thunderstorms and of other local storms. It 
is well known that tornadoes are generally connected with a decided fall of tem- 
perature in the northwest quadrant of the cyclone within which the tornadoes 
are formed; and that thunderstorms are usually followed by colder weather. On 
account of the rapid flow of the upper currents, which may bring the advancing 
upper edge of the cold wave over warmer air, these conditions attending local 
storms favor the formation of the cold wave type of curve, such as was shown by 
our kite records on the afternoon of August 31, 1895, preceding an energetic 
thunderstorm on the evening of the same day. 

Type 6, Plate VII., plotted from the records of the kite meteorograph for 
September 8, 1896, shows a less common but an interesting form of vertical 
distribution of temperature, in which the temperature was virtually the same from 
400 to 1,400 meters or more. In other words, there is no change, or a very small 
change, of temperature with increasing altitude above 400 meters or thereabout. 
Below this level, Type 6 shows the same form as Type 1 and Type 2; that is, a 
fall of temperature with increasing altitude during the day, and a rise with increas- 
ing altitude at night. These last conditions can be readily traced to the effects of 
insolation and radiation near the ground. Suppose, for example, that at a certain 
hour of the morning the temperature of the air were the same from the ground: 
up to 1,000 meters or more. (The thermograph records at the Valley and at the 
Summit Station show that this occurred at 8:15 4. mM. on September 8.) After this 
time the temperature at the ground will rise because of the heating by insolation. 
The air next the ground, being heated by contact, will rise and cool by expansion 
until it assumes the temperature of the air aloft, which is not then heated. This 
process must continue until the maximum temperature of the day is reached. On 
September 8, the rise of temperature from 8:15 a.m. to the maximum temperature 
of the afternoon at the Valley Station was 8° F. Hence, at the warmest part of the 
day, the air next the ground, rising and cooling at the rate of 1°.8 F. for each 100 
meters of ascent, would rise to 444 meters before falling to the temperature observed 
at 8:15 a, M., which is assumed to be the mean temperature of the upper air column. 
In almost every case of this type of curve, the limit of the adiabatic rate of fall, 
and hence of the ascending currents during the day hours, was found to be near 
400 meters; which shows that the conditions of September 8 were normal conditions. 
At night, cooling takes place by radiation next the ground. It is gradually trans- 
mitted upward a few hundred meters by conduction, thus producing an increasing 


114 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


temperature with increasing altitude. Before sunrise on the morning of September 
8, the temperature was 8° F. warmer at the top of Blue Hill than at the Valley 
Station. As a result of the conditions described, it is evident that, on days like 
that under consideration, the diurnal range of temperature is not felt above 500 
meters, unless the upper air itself is directly heated by insolation and cooled by 
radiation; but observation proves that this does not take place except to a very 
small degree. 

Examples of the different types are found on the following days: — 

Type 1. September 21, 1895; May 4, June 19, June 22, June 29, July 23, 
August 26, and November 17, 1896. 

Type 2. March 11, July 20, July 22, and August 31, 1896. 

Type 3. November 23, December 21, and December 26, 1895; January 12 
and February 23, 1896. 

Type 4. December 9, 1895; February 13, April 13, April 18, April 27, May 9, 
August 1, September 17, September 29, October 8, December 12, 1896; and 
January 2, 1897.. 

Type 5. August 51, November 20, November 27, November 30, December 12, 
1895; January 27, February 17, December 15, 1896; and February 10, 1897. 

Type 6. (a) March 6, (4) April 15, (c) April 24, (d) May 7, (e) May 20, 
(f) June 6, (g) September 8, and (4) November 30, 1896. 

In most of the short ascents the curves are probably those of Type 1 and 
Type 2; but the altitudes reached were too low to determine to which type each 


curve belongs. 


Tyres oF Humipiry CHANGE WITH ALTITUDE. 


The different types of humidity curves, showing the changes of humidity with 
altitude, derived from the. records of the kite meteorograph, are given in Plate VII. 
These curves are plotted from the records on selected days, in order to show each 
type. As in the preceding plates, the continuous lines represent the records of the 
ascent, and the broken lines represent the records of the descent. 

Type 1 and Type 2 may be called the normal types of curves when clouds 
are present. Type 1 is plotted from the records of August 31, 1896. On this 
day, the ascent was shortly before noon, and is shown by the continuous curve. 
There are no records of the descent. Hence, the broken curve is plotted from 
the records of other dates in order to illustrate the night form of the curve. 
Type 2 is plotted from the record of October 8, 1896, and is shown in Plate V. 
It differs from Type 1 in showing in its upper part a fall of humidity rather 


EXPLORATION OF THE AIR BY MEANS OF KITES. 115 


than a rise. The form which the curve takes at night had not become fully 
established at the time of the descent on October 8, but it is probably like the 
form given in Type 1. These two types of curves can be described as the normal 
types of change of humidity with change of altitude in cloudy or partly cloudy 
weather. The humidity increases steadily after leaving the ground until the base 
of the cloud is reached ; then the hygrograph shows complete saturation, or 100 per 
cent. This condition continues to the top of the cloud; then occurs a sudden and 
marked fall of humidity as the meteorograph passes into the dry air above the 
cloud into which the ascending currents from the ground have not penetrated. 
After entering this dry air, the hygrograph sometimes shows a fall and sometimes 
arise of humidity with increasing altitude, as represented in Type 1 and Type 2. 

Type 3, plotted from the records of August 1, 1896, is a clear-weather type of 
curve in which the humidity rises until a certain altitude is reached, probably at 
the upper limit of the currents ascending from the ground. Above this altitude, 
the humidity falls rapidly. 

Type 5, plotted from the records of January 19, is also a clear-weather type ; 
and since this type occurs almost exclusively on the same days as Type 5 of 
temperature, it is numbered the same. In other words, the clear-weather type is 
the accompaniment of cold waves, in which very dry descending air is mingled 
with air rendered damp by ascent. The result is a nearly uniform relative 
humidity at different altitudes, though of course the absolute humidity diminishes 
with increasing altitude on account of the diminishing pressure and temperature. 

Type 6 is plotted from the records of September 8, 1896. In this type, both 
the relative and the absolute humidity diminish rapidly with increasing altitude, 
except very near the ground and during the daytime when ascending currents 
are in progress. Its dates of occurrence coincide almost exactly with the dates of 
Type 6 of temperature. It is therefore numbered in the same way. As shown in 
the next section, this type of temperature and humidity is found near the central 
area of anticyclones. In Types 1 to 3, the absolute humidity remains nearly 
stationary, or falls slowly until the cloud level, or the point of maximum relative 
humidity, is reached; after this, it falls rapidly. 


PosITIONS OF THE DIFFERENT TyPES OF VERTICAL DISTRIBUTION OF TEMPERATURE 
IN CYCLONES AND ANTICYCLONES. 


In order to ascertain the relation of the types of vertical distribution of* tem- 
perature to cyclones and to anticyclones, the position of the centre of the cyclone 


116 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


or the anticyclone prevailing at the time when the kite ascended is taken from 
the map of the United States Weather Bureau for the given date, or from the 
map of tracks in the Monthly Weather Review. The numerals representing the 
different types shown in Plate VII. are then plotted in a chart in their proper 
position as regards the centre of the cyclone and the anticyclone. These charts 
are shown in Plate I. Figures 3 and 4. The small figures represent the numbers 
of the different types. The figures in parentheses accompanying Type 3 show in 
meters the approximate altitudes of the maximum temperature, which in this type 
occurs at a moderate distance above the ground. The figures in parentheses ac- 
companying ‘Type 4 show in meters the approximate altitude of the sudden rise 
of temperature found in this type. The letters in parentheses accompanying Type 6 
refer to the letters on page 114, accompanying the date of each example of this 
type. They are for use in reference, on account of the interest of this type. The 
small circle with a dot in it, near the middle of each chart, gives the position of 
the centre of the cyclone or the anticyclone. Distances are shown by the scale 
at the foot of the charts. The average width of the cyclonic and the anticyclonic 
circulation of the wind is shown in these Annals, Vol. XXX. Part IV., Plate XIV. 
Figures 2 and 5. 

Type 1 does not appear on the charts; in other words, it is non-cyclonic in its 
character. 

Type 2 occurs in the cyclone to the east and southeast of the centre, but is 
not found in the anticyclone. 

Type 3 occurs exclusively in the southeast quadrant of the cyclone; and the 
continuous curve encloses all the cases observed. ‘Type 3, however, was observed 
only in the winter half-year; during the summer half-year it was replaced by 
Type 2. 

Type 4 and Type 5 were found chiefly within anticyclones, and Type 6 was 
found entirely within them. These types occur in groups in different positions 
about the centre of the anticyclone. Straight lines are drawn in the chart to 
separate the groups. 

Type 5, the cold wave type, is found chiefly in the southeast quadrant of the 
anticyclone. Two cases occurred south of the centre of the cyclone, slightly in 
advance of the position where Mr. R. DeC. Ward found the maximum frequency 
of thunderstorms in cyclones over New England. (Harvard Annals, Vol. XXX. 
Part IV., Plate XIV. Figure 6.) Type 3 and Type 5 follow opposite courses near 
the ground, one showing a rise of temperature with altitude above the ground; the 


other showing an abnormally rapid fall. It is interesting to note that Type 3 is 


EXPLORATION OF THE AIR BY MEANS OF KITES. Vea 


found in the southeast quadrant of cyclones, and Type 5 in the southeast quadrant 
of anticyclones. In both cases, the position is such that the winds are crossing the 
lines of latitude nearly perpendicularly. (Harvard Annals, Vol. XXX. Part IV., 
Plate XIV. Figures 2 and 5.) In the first case, the winds are moving from a warmer 
to a colder latitude, and hence are chilled by contact with the colder ground; in 
the second case, the winds are moving from a colder to a warmer latitude, and 
hence are abnormally warmed by contact with the ground. 

Type 6 is of especial interest on account of its form and position, and its 
bearing on the theory of the anticyclone. The records of the kite meteorograph, 
as illustrated by these curves (Plate VII. Type 6), show the same conditions 
aloft near the central area of anticyclones as are found at the meteorological 
observatories of Kurope; namely, a warm and very dry air. The observations at 
the Alpine observatories, and especially on the Sonnblick, have been ably discussed 
by Dr. Hann. The warm and extremely dry air at altitudes of a kilometer and 
higher, near the centre of anticyclones, is generally explained as being the result 
of the warming of the air by descent and consequent compression. This ex- 
planation demands that the air shall be heated by descent at the adiabatic rate. 
In other words, in ascending into the air the temperature should fall at the adia- 
batic rate. This condition might be modified near the ground by cooling from 
radiation of heat to the ground, by contact with the ground, or by conduction of 
heat to the ground, provided that in each case the ground is cooler than the air. 
But during the daytime, when the ground, and the air immediately above it, are 
warmer than the mean temperature of the air column, as shown by the lower 
part of the curve of September 8 (see Plate VII. Type 6), these supposed modi- 
fying causes entirely fail to explain the matter. Hence, with the condition of 
no temperature change with change of altitude, shown by the records of the 
kite meteorograph, either there can be no descending current below 1,500 meters 
near the centre of the anticyclone, or there is some cause (or causes) other 
than those given above which counteract the dynamic heating of the air by 
descent. 

Mr. R. DeC. Ward, with whom I discussed the diagrams, suggested the cause 
to be the mixing of air currents of different temperatures. The temperature of 
the air on the east side of the central area of the anticyclone changes with 
change of altitude, at the adiabatic rate approximately; on the west side, it 
changes at the adiabatic rate during the warmest part of the day up to a certain 
altitude, where there is a sudden rise of temperature, and above that altitude a 
slow decrease with increasing altitude. It is possible that these two conditions, 


118 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


in which a fall of temperature with increasing altitude is the prevailing character- 
istic, could, at their place of meeting, bring about a condition of no change of 
temperature with change of altitude. But it is difficult to understand the pro- 
cesses. It is also difficult to conceive of the mixture of ascending and descending 
currents in the central area of the anticyclone without adiabatic change with — 
change of altitude. The overflow of air in the anticyclone appears to demand a 
descending current near the central area. But since this seems inconsistent with 
the condition of no change of temperature with change of altitude, there appears 
as yet no adequate explanation of the condition; and especially so, since the air 
is known to cool with extreme slowness by radiation. The radiation into space 
would be more effective at the high altitudes from which the air starts than near 
the ground. Furthermore, on some of the days showing this type, as on September 
8, the sky was covered with cirro-stratus; yet the condition of no change or a 
very slow change of temperature with change of altitude in the positions shown 
by Type 6 in Plate I., Figure 3, remained the same as on clear days. 


CHANGES OF TEMPERATURE WITH ALTITUDE IN CYCLONES AND ANTICYCLONES. 


The distribution around the centres of cyclones and anticyclones of the types of 
temperature change with change of altitude shows, in a general way, the differences 
of temperature between any given levels in different parts of the cyclone and the 
anticyclone. In order to study the differences more in detail, charts were made to 
show the differences between each 300 meters of altitude. Since the changes of 
temperature with altitude during the day differ from those during the night, and 
the changes with altitude during the winter differ from those during the summer, 
the number of charts showing all the conditions is considerable, and it is not deemed 
expedient to publish them. The striking features brought out by them are that 
southeast of a line running from southwest to northeast, and passing about 400 kilo- 
meters to the east of the anticyclone centre, the fall of temperature with increasing 
altitude in the anticyclone is faster than in any part of the cyclone; and it approxi- 
mates, or slightly exceeds, the adiabatic rate in unsaturated air. Within 300 meters 
of the ground around, and 500 kilometers to the southeast of the centre of the 
anticyclone during the day, the rate of fall of temperature with increasing altitude 
equals 2°.6 F., or 1°.5C., for each 100 meters of altitude, this being the greatest 
rate of fall yet recorded. Northwest of a line running from northeast to southwest 
and passing about 400 kilometers west of the centre of the anticyclone, the temper- 
ature was found to be higher at all altitudes from about 300 to 1,000 meters 


EXPLORATION OF THE AIR BY MEANS OF KITES. 119 


than it was at the same time at the ground. The western limit of this area of 
high temperature aloft was not shown in the charts. 

Over a considerable area, central about 800 to 1,000 kilometers southeast of the 
centre of the cyclone, the temperature at the height of 300 meters during the 
winter half-year was higher than at the ground; and during the summer half-year, 
the rate of change of temperature with change of altitude was usually less than the 
adiabatic rate. Between the altitudes of 300 and 600 meters, the rate of change 
of temperature during the day was found to approximate very closely to the adiabatic 
rate in unsaturated air; except that over an area to the east of the cyclone centre, 
where rain was falling and cloud formation had begun below 600 meters, (See area 
of nimbus cloud in average cyclone, Harvard Annals, Vol. XXX. Part IV., Plate IV. 
Figure 2.) Few records were obtained above 600 meters to the east and north of 
the cyclone centre; but in these few cases cloud formation had begun between 
this altitude and 1,000 meters, and the change of temperature with change of alti- 
tude was slow. A number of records between 600 and 1,000 meters was obtained 
south of a line passing about 500 kilometers south of the centre of the cyclone. 
In most of these, the change of temperature with change of altitude during the 


day approximated to the adiabatic rate. 


VERTICAL GRADIENT OF TEMPERATURE ON DAYS witH CUMULUS CLOUDS. 


Cumulus clouds have frequently been explained as originating in the heated air 
which rises from the ground, and which is cooled by expansion till its contained 
vapor is condensed. If this is true, the ascending air must cool at the adiabatic 
rate, and the air which descends to take its place must also be heated by descent 
at the adiabatic rate; thus it is of interest to determine how near this rate of change 
of temperature with change of altitude is shown by the records on days when 
cumulus clouds prevailed. 

Table XX VI. gives the differences in temperature, and also the rates of change 
of temperature per 100 meters, between the Valley Station and the kite mete- 
orograph, when the latter was about 500 meters high on days with cumulus 
clouds. Table XXVII. gives the differences and the rates of change on days with 
cumulus clouds when the kite meteorograph was about 1,000 meters high. By 
classifying the rates of decrease per 100 meters in Table XXVI. and Table XXVII. 
according to the hours of the day, Table XXVIII. is obtained, where the rates in 
Table XXVI. are also classed according to season. 


120 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


TABLE XXVI. 


CHANGES OF TEMPERATURE WITH ALTITUDE FROM 0 TO ABOUT 500 METERS, ON DAYS 
WITH CUMULUS CLOUDS. 


Alt.of} Temp. | Rate Alt. of mp. | Rate Alt. of | Temp. 

Date. Hour. Kite Diff. | per 100 Date. Kite per 100 Date. Kite Diff. 
above} Valley | Meters above Ih Meters. above | Valley 

Valley.| to Kite. 7 Valley.| to Kite. Valley.| to Kite. 


1895. met, or oR 1896. met. ok. oF. | 1896. _ met. oF. 
Aug. 20 |11:20 a | 452 7.7 ,—1.7] May 3:20 P| 480 8.3 |— 1.7] Sept. 511 |—12.7 
Aug. 24} 0:46 pe} 540 9.8 |— 1.8 | May 3:04 P| 558 ced po 478 |— 10.0 

a Osmeiase 9.2/—1.9] * 5:17 P| 568 — 1.2] Sept. 425 |— 10.9 
Aug. 26| 3:57 p| 546 7.4|—1.4] May 3:13 P| 472 4 lane. bd epke 463 |— 9.0 

p “ 5:37 p| 501 3.2 |— 0.6 | May 4:58 p| 559 6|—1.4] “ 504}/+ 4.2 
Ang. 28} 4:45 p| 488 6.4/—1.3]June 4:20 pe | 560 —1.9] Sept. 2 5387 |— 14.2 
Aug. 31| 0:05 p| 487 —21} * 6:23 P| 480 1.91 500 |— 3.6 
Sept. 2:18 P| 533 —1.5}]June 5:21 p| 5384 Behl lates : 611 |—10.1 

June 2:29 p| 381 4/—1.9 528 8.6 

3:33 P| 558 --1.8] July 2:56 Pp} 520 —1.8 551 9.0 

5:29 p| 491 8 /—1.2] July 2:38 p| 484 ; 650 1.3 
Feb. 12| 5:34 P] 562 8.8 |— 1.6] July 1:48 P| 548 8] Oct. : 498 8.4 

| Feb. 4:40 p —2.1 2:45 p| 482 . 418 5.8 
Apr. 4:26 p ) — 128 3:36 P| 478 ‘ : 473 7.6 

4 6:24 P 8 7 |—1.4 6:15 P| 510 : : 467 3.8 

June 18) 5:21 P —2.0 11:00 a | 556 
i June 19| 2:42 p| 4¢ —2.1 4:18 p| 511 : j 605 
3:07 P : —1.9 9:42 P| 560 ! 552 
Spilsise ll ie —1.9 ; 10:16 a | 496 2. 576 
Apr. 13} 3:54pP a its) : 4:54 p | 475 : : 640 
May 4| 2:18 P| 53: 3/-1.8 5:31 pe | 471 | 


TABLE XXVII. 


CHANGES OF TEMPERATURE WITH ALTITUDE FROM 0 TO ABOUT 1,000 METERS, ON DAYS 
WITH CUMULUS CLOUDS. 


a of Shy Rate Alt. of mp. Rate Alt. of 
ae per 100 ate. -| Kite per 100 Date. .| Kite 

above Meters. -M. | above Meters. above aK 
Valley. Valley. Valley.| to Kite. 


meters. Ou é : meters. oF; oF, 1897. meters, ae 
1060 |} —12.0 : ‘ 1065 | —17.7| —1.7] Jan. 19 1011) —19.9 
1089 | — 5.7 it 863 | —11.6| —1.4] Feb. 9 1018 | —18.6 


827 | —16.0 é p 940} —15.9| —1.7] Feb. 10 990 | —16.2 
June 2 1084 | —19.9 8 g. 1041 | —19.2);--1.8] “ a 990 | —10.7 
June 29 1037 | —16.2 : 925} — 2.4} —0.3 


July 10 SO hs ; t. SIE | agit eal 
July 23 858 | —14.5 ; 2 983 | —12.6] —1.3 


EXPLORATION OF THE AIR BY MEANS OF KITES. 121 


TABLE XXVIII. 


DECREASE OF TEMPERATURE, IN DEGREES FAHRENHEIT PER HUNDRED METERS, AT 
DIFFERENT HOURS ON DAYS WITH CUMULUS CLOUDS. 


Valley to Kite at 500 Meters. — May to August. 


A.M. P.M. 

‘peal? |) eat | see: | 2-3 3-4 4-5 5-6 6-7 1-8 9-10 
lie 1.8 1.9 2.1 1.4? 1.3? 0.6? + 0.5 
its 2.1 21 1.8 i) 2.0 1.9 


Means -|/ 1.7. | 2.0.) 1.95) 2.0 1.9 1.8 Lip 1.6 


Valley to Kite at 500 Meters. — November to February. 


A.M. PEM 


11-12 | 12-1 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 


iL 0.9 
ye [Fee eh ee SS Re 
Means 1.8 a2, 


Valley to Kite at 1,000 Meters. — Year. 


A.M. P.M. 
11-12 | 12-1 | 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 
tikes Tales fea 1.6 19 1B | 0.5 0.8 
Tee mek. 1.8 1.8 1.4 
2.0 Led 1.3 1.1 
1.8 1.6 
Means L&ajrii 1.7 Lf 1.5 1.0 0.3 


Norr. — A question mark (?) indicates observations made in 1895, when a weekly clock cylinder 
was used on the thermograph at the Valley Station. The figures thus marked are considered un- 
trustworthy, and are not used in the means. The sign + indicates that the temperature was higher 
at the kites than at the ground. 


A striking feature of Table XXVIII. is that the means show a maximum rate of 
change of temperature with change of altitude near the warmest part of the day, 
and a small rate of change after sunset. In the only observation after 9 p.m. at 


122 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


500 meters, the sign was reversed, showing the air to be warmer at that altitude 
than at the Valley Station. The average rate appears to equal or to exceed slightly 
the adiabatic rate during the daytime, at least until 5 P. M. 

Dr. Hann, in his well known treatise on Die Gesetze der Temperatur-Aen- 
derungen in Aufsteigenden Luftstrémungen, etc., computes the adiabatic rate of 
cooling in dry air to be 0°.009907 C. for each meter of ascent, and says: “ Therefore 
the cooling of the ascending air amounts almost exactly to 1°C. for every 100 meters, 
and it remains the same from whatever level the ascent begins or whatever the 
initial temperature may be. On the other hand, a descending air stream becomes 
1°C. warmer for each 100 meters.’ (Zeitschrift der Oesterreichischen Gesellschaft 
fiir Meteorologie, Vol. IX. p. 323.) 

He shows that this rate is somewhat diminished by moisture in the air, and, as 
an example, computes that ascending air with an initial temperature of 30° C., a 
relative humidity of 60 per cent, and consequently a vapor tension of 18.9 mm., 
would cool at the rate of 0°.009751C. for each meter of ascent, which is equivalent 
to a decrease of 1°.755F. for each 100 meters of ascent. In Recent Advances in 
Meteorology (Report of the Chief Signal Officer, 1885, Part II.), Ferrel discusses 
the problem of the adiabatic rate in dry air. He computes the rate of change as 
0’.00979 x for each meter of ascent or descent; in this result the factor n causes 
the rate to diminish slightly with latitude south of 45°, and also with altitude. 
Since the adiabatic rate in moist air is slightly less than in dry air, this computation 
would make the normal rate of cooling in moist but unsaturated air somewhat less 
than 1°.76 F. for each 100 meters of ascent, probably about 1°.74 F. Professors Abbe 
and Bigelow, who were consulted in regard to the formula, suggest an additional 
term due to the direct heating of the air by insolation after it leaves the ground. 
The absence of any appreciable diurnal period above 1,000 meters arising from 
the direct effect of insolation and radiation on the air, prove, I think, that this 


term is negligible. 
CoMPUTATION OF THE HEIGHTS OF CLOUDS By MEANS oF THE DeEw-PorntT. 


Fifty-six years ago Espy pointed out the possibility of computing the altitude 
of the base of cumulus clouds from the difference in temperature between the 
air and the dew-point. He proved that his computation was approximately correct 
by sending up a kite into the base of the cloud, thus determining its altitude. 
(Espy’s Philosophy of Storms, p. 75.) 

It is of interest to compare the altitudes of the bases of clouds measured by 
kites at Blue Hill with the altitudes computed from the differences between the 


EXPLORATION OF THE AIR BY MEANS OF KITES. 123 


air temperature and the dew-point, using the more exact determination of the 
adiabatic rate by Hann and Ferrel. Besides knowing the adiabatic rate, it is also 
necessary to know in these computations the rate of change of the dew-point with 
altitude when the air is expanding adiabatically. This rate of change Professor 
W. M. Davis gives as 0°.2C.(0°.356 F.) for each 100 meters. (Elementary Meteorol- 
ogy, p. 163.) Hence 0°.0176 F. (the adiabatic rate of cooling for each meter of ascent 
given by Ferrel) less 0°.0036 F. (the fall of the dew-point for each meter), divided 
into the difference between the air temperature and the dew-point, ought to give, 
approximately, the altitude at which the air is cooled by expansion to the tem- 
perature of the dew-point and condensation into cloud particles begins. In this, 
the small corrections for latitude and moisture are neglected, and the formula 


d.b.—d. p. , ; 
becomes “Se = altitude of base of cloud. In this d. b. is the temperature 


shown by the dry-bulb thermometer, and d. p. is the dew-point. This agrees 
with the formula in Davis’s Elementary Meteorology (page 163), which is 
(1.6—0.3) x 300 ft. 

Table XXIX. gives the observed heights of clouds in meters as measured by 
kites, the heights computed by the preceding formula, and their differences. 

Table XXX. shows these differences between the observed and the computed 
heights, classified according to the hours of the day and also according to the meas- 
ured altitudes of the cloud. The altitudes in these tables are above the level of 
the top of Blue Hill, and not above the level of the Valley Station, as in the 
preceding tables. 

In these tables not only cumulus, but also strato-cumulus, stratus, and nimbus, 
are included in the investigation, and the heights computed from the differences 
between the air temperature and the dew-point agree in a general way with the 
measured heights of all these different cloud forms. 

When the differences between the observed and the computed heights are clas- 
sified according to the hours of the day, as in Table XXX., the computed altitudes 
average lower than the observed altitudes until noon; between noon and 2 Pp, M, 
the two are nearly the same; and after 2 p.., the computed exceed the observed 
heights by differences which rapidly increase as evening approaches. It is well 
known that the difference between the air temperature and the dew-point increases 
until the warmest part of the day, and then diminishes until the coldest ; hence 
the best explanation of the observed facts is that the vapor from which the cloud 
is formed left the surface of the ground some time previously. 


124 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


TABLE XXIX. 


HEIGHTS OF CLOUDS MEASURED BY KITES COMPARED WITH HEIGHTS COMPUTED 
FROM THE DEW-POINT. 


Kind of |Observed eae Mae Date. Hoan Kind of |Observed a Obnetree 
Cloud. | Height. | eight, Computed. Cloud. | Height. | Freight. ‘Computed. 


“meters. meters. | meters. 1896. meters. | meters. | meters. 

10:38 a 661 | 686 25 | Oct. 4:34Pe | scu | 1344 | 985 | +359 
1:43 P 809 | 842 3: Regt 356 5:23 P « 1370 | 857 | +518 | 

10:54 a 1187 | 1214 Dec. 15 | 2:23 P sé 530 | 428 | +102 
1:58 P 1178 | 1143 ts 
2:05 P 1224 | 1136 Nov. 23 | 11:30 4 61 | 456 | —395 
3:31 P 1420 | 11138 Dec. 9| 9:494 138 | 164 
4:00 P 410 | 414 Aeon 
9:40 a 190 | 207 4 | May 22 | 8:304 107 00 
9:47 A 198 | 249 aha! 8:55 A 175 00 
9:46 a : 290 | 421 July 3 | 3:50P 243 | 157 
2:30 P 244 | 292 Oct. 31 79:20 282 | 456 
3:00 P 242 | 271 pt bk ta 9:25 A 354 | 464 
4:53 P 232 | 164 Nov. 18 | 0:29p 383 | 285 
2:33 P 425 | 514 0:46 P 331 | 292 


4:35 P 393 | 321 


5:18 P 339 | 207 : 11:55 a 821 | 342 
4:01 P 454 | 378 0:01 P 334 | 349 
4:15 P 361 | 342 1:00 P 324 | 342 
10:22 a 411 | 578 
0:15 P 321 | 507 ) 10:50 4 197 | 200 
3:17 P 287 | 299 ‘ 2:15 P 30 00 
2:52 P 660 | 456 : 2:45 p 178 | 222 
3:00 P 610 | 450 11:56 a 401 | 328 
3:34 P 784 | 357 2 9:10 a 165 | 143 
3:53 P 245 | 242 y 4:12e | n@° | 1108 | 778 
10:25 291 | 242 . 3:00 P {Nn 260 | 157 
11:26 a 476 | 364 10:38 a N 297 | 285 
11:45 a 333 | 235 9:10 4 312 | 214 
0:42 P 422 | 292 2 10:01 4 340 | 285 
2:39 P 1541 | 1148 A 8:25 a 235 | 157 
3:01 P 1454 | 1148 - 1:50 p 277 | 228 
3:34 P 1360 | 1100 C. 9:28 a 66 14 


In this table cu = cumulus, s cu = strato-cumulus, s = stratus, fs = fracto-stratus, N = nimbus, 
f Nn = fracto-nimbus, %° = light snow, @° = light rain. 


In computing the heights in Table XXIX., the difference between the air tem- 
perature and the dew-point was taken in each case at the time of the measurement 
of the cloud heights, when, to be more exact, it should have been taken some time 
earlier, in order to get the conditions of the ascending air within which the cloud 


EXPLORATION OF THE AIR BY MEANS OF KITES. 125 


TABLE XXX. 


DIFFERENCES BETWEEN OBSERVED AND COMPUTED HEIGHTS OF CLOUDS, IN METERS. 


At Different Hours. 


A.M. 


9.00 10.00 
to 0 
9.59. 10.59. 


— 17 
— dl 
—131 
— 26 
—174 
—110 
+ 22 
se 08 
+ 52 


+13 +9 ) 2 {-FISt | +323 


At Different Altitudes. 


700 900 1000 | 1100 1200 
to F to to to to 
799. A 999, | 1099. | 1199. | 1299. 


—71)|+88 
aes +35 


was formed. In the morning the computed heights would have been lower, and 
in the afternoon higher, than those given; thus agreeing better in each case with 
the measured heights. 

The mean difference between the observed and the computed altitude of the 
cloud between 9 a.m. and 11 a.m. is found to be 32 meters, the computed height 
being higher. In order to lower the mean computed heights by this amount, it 
is necessary to subtract 0°.6 F. from the difference between the air temperature and 
the dew-point at the time of the measurements of the clouds. The mean increase 


126 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


of temperature found at Blue Hill between 9 and 1] a.m. is 3°.3F.; while the 
mean change in the dew-point for the same interval is virtually zero. Therefore 
at this rate of increase it would be necessary to take the atmospheric’ conditions 
prevailing 22 minutes earlier in order to diminish the difference between the air tem- 
perature and the dew-point 0°.6 F. Now the mean height of the clouds from which 
the differences were taken is 337 meters. Supposing that the air rises this distance 
in 22 minutes, the rate of ascent would be 15 meters per minute, or about 0.3 meter 
per second. In order to correct the computed height to the observed height, about 
10 meters must be subtracted for each 100 meters of the computed height. How- 
ever, in the afternoon, in order to make the computed height, even as late as 
5 p.M., agree with the observed height, it is necessary to use the temperature and 
the dew-point prevailing near the warmest part of the day. It is shown in some 
of the earlier investigations in this discussion (page 99) that the adiabatic rate of 
change of temperature with change of altitude ceases soon after the warmest part 
of the day, and it is safe to infer that cloud formation from local ascending currents 
ceases about this time in ordinary conditions, and that the clouds remaining later 
are slowly subsiding under the influence of gravity, and are dissipating, provided 
no other causes are active in their formation, as is the case with nimbus and stratus. 

Applying no correction to the morning observations, and omitting all results 
after 3 p.M. for the reason just given, the differences between the measured and 
the computed heights of the clouds are classified in Table XXX. according to 
altitude, using successive intervals of 100 meters each. The results show that most 
of the clouds measured by the kites were low clouds, the position of maximum 
frequency being about 350 meters above the top of Blue Hill; or, in round numbers, 
about 500 meters above the Valley Station. The means at the foot of the table 
show that the measured heights were less than the computed heights at the lowest 
altitudes, and greater than the computed ones at the highest altitudes. This is 
because clouds were found at the lowest altitudes chiefly in the morning and at the 
highest altitudes in the afternoon, as shown by the following average heights, in 


ineters : — 
A.M. P.M. 
9.00 10.00 11.00 12.00 1.00 2.00 3.00 4.00 
Hour. to to to to to to to to 
9.59 10.59 11.59 0.59 1.59 2.59 8.59 4.59 


Mean altitude of ) 


} 222, 476 318 860 647 592 710 612 
cloud in meters 5 


However, the chief interest is not in the means given in the table, in which 
the + and the — sign partly neutralize each other, but it is in the means of the 
differences without regard to sign. These are as follows : — 


EXPLORATION OF THE AIR BY MEANS OF KITES. 127 


Altitude in 


to to to to to to to to to to to to to 
meters 


00 100 200 300 400 500 600 700 800 900 1000 1100 1200 13800 
t 
99° 199 299 399 499 599 699 799 899 999 1099 1199 1299 1399 


Mean of yee 62 74 113 99 
ferences 
Per cent Rha 18 19 25 8 
altitude 


This shows that the mean error in computing the cloud heights by the formula 
given on page 123 is about 18 per cent for the low clouds, which were stratus, 
strato-cumulus, and nimbus. However, this also includes the errors in the measure- 
ments of the base of the clouds by the kites, so that the probable error of the de- 
termination of the cloud height by the formula presumably does not exceed about 
10 per cent. Refinements by the use of the factors omitted from the formula, and 
by taking as a basis the conditions of the air when it left the ground, and not the 
conditions at the ground when the cloud was measured, will no doubt greatly 
improve this result. In the case of stratus and nimbus clouds, the air is probably 
ascending very obliquely, so that some correction may possibly be needed for change 
of latitude or of environment. For example, the air in which floats the nimbus cloud 
observed overhead may have ascended from the ground 50 kilometers distant from 
the station over which it is observed. 

The mean error of the computed heights of the cumulus clouds which were 
found between 1,100 and 1,400 meters is considerably less, relatively, than that found 
for the lower clouds, because it averages only 8 per cent of the altitude. But this 
difference is a compound of the errors of measurement and of the errors in the 
computed heights; so that the probable error of any computed altitude by the 
formula described presumably does not exceed 5 or 6 per cent of the true height. 
The error of measurement includes not merely the error of determining the height 
of the kites, which is very small, but it includes also the error of determining when 
the kites enter the base of the clouds. This error may be considerable, because the 
kites in some cases rise between passing clouds, and higher than their bases, before 
the cloud is entered. When the distance above the base was short, it could not 
always be determined (owing to perspective) whether the kites entered the cloud 
at the base or slightly above it; especially if the bases were more or less irregular 
and indeterminate, as sometimes happened. The differences of level between the 
bases of adjoining clouds sometimes amounted apparently to as much as 1 per cent 
of the altitude. 

Hence the conclusion drawn from this investigation is that the difference in tem- 
perature between the air and the dew-point furnishes an easy and fairly trustworthy 


128 BLUE HILL METEOROLOGICAL OBSERVATIONS. 


method of determining the heights of clouds below 1,500 meters. The probable 
error of any determination in the case of low clouds will be perhaps 100 meters. 
But if the computations of height are confined to the warmest part of the day 
(between 1 and 2 p. M.), the results at Blue Hill indicate that the mean error of a 
number of cases will be less than 2 per cent of the altitude, an accuracy equal to 
that of measurements by theodolites. ‘This determination, however, is subject to the 
reservation that the clouds must be moving in approximately the same direction as 
the surface wind, otherwise the conditions may be very different at the cloud and 
at the ground. For example, if a sea-breeze is blowing at the ground, it would be 
impossible to compute the altitude of cumulus, which is seen at a distance, and which 
may be forming at the edge of the sea-breeze over a heated land surface. 


ALTITUDES OF THE KITES WHEN ELECTRICITY Was First NorIceD. 


After the introduction of wire for a kite line, electric shocks were received from 
the wire, and sparks 2 to 5 mm. in length were occasionally seen when a conductor 
was brought near the wire. The wire was not insulated except by the wooden stand 
on which the -reel was placed; but when the kites were at great altitudes, the elec- 
tricity at times became so unpleasant that it was necessary to make a connection 
with the ground. The altitudes of the upper end of the kite line, when electrical 
effects were first noticed, were variable, and, to a certain extent, evidently dependent 
on the weather. Thus in snowstorms, electricity was much more active than in other 
weather.- No ascents were made very near thunderstorms, except on May 11, 1896, 
when the kites were drawn down rapidly as a thunderstorm approached from the 
west, and on May 19, when the kites were sent up after the passage of a thunder- 
storm. In both cases the altitude was small, and only in the first case were strong 
shocks felt. The dates and altitudes at which strong electrical effects were noticed 
will be found in the Remarks following Tables XVII. and XVIII. Variations in the 
amount of wire on the reel, and changes in its insulation, no doubt affect the altitude 
at which electricity is noticeable. Therefore the altitudes cannot be taken as entirely 
trustworthy indications of the relation of electrical potential to weather conditions, 
although the electricity became much stronger in snowstorms and near thunder- 
storms, as previously mentioned. In the majority of cases, the altitude of the top of 
the line when electricity was first noticed was about 500 meters, and the potential 


increased with height. 


Mr. Fergusson and I are indebted to Mr. H. 8. Mackintosh for a careful revision 
of our manuscripts. 


END OF VOLUME XLII. PART I. 


PLATA ak 


DISTRI UCN Ones PE Gls BOUDEEOR IMS: 
ANTI-CYCLONES. CryiGlONES: 


SE 


ULUs AND STRATUS L VELS, 


| I 
ALTO-CUMULUS SQUAMOSUS. 


UNDULATIONS INCUM 


CUMULUS CHANGING UNDULATIONS, 
TO ALTO;CUMULUS. 
is J 


DISTRIBUTION, OF SL EMPERATURE TYPES. 
ANTI-CYCLONES. CrCeONES: 


eel 


° 
CENTRE 


DISTANCES. 
——_—_——_ 


KILOMETERS. 


PLATE II. 


Fic. 6, 
Ire. 76 


‘ PLATE Ili. 


a vale 


2) cain o< 


PA ee LV 


TEMPERATURE. 


HUMIDITY. 


FS EE ey METERS 
EE i 


HEIGHT, 


eet == =e 
SeScseene SSS AL 


CENTIMETERS. 


i 
— 
ty 


=» = 7 
wae 


lee 


ey 


PEATE, Vz 


DIURNAL RANGES, MEAN WIND VELOCITY. 


TEMPERATURE, 


-10 -15 PerCent. 9 Met.perSsec.8 


ASCENT \OF OCTOBER 8 1896, 


TEMPERATURE. HUMIDITY, 


o° to° 


dec. { 256 26° 29° 32° 35° 38° EMA ASe AT 50: 60 Per Cent 70 O°Az. +20° +40° 


PLATE VI. 


METERS. i METERS 
1800 7 7 : ' 1800 
Foo S\MULTANEOUS "TEMPERATURES, OCT. 8 1896. 1700 

; GP My . 
1600 : 1600 
1500 1500 
1400 1400 
1300 1300 
1200 1200 
1100 1100 
1000 1000 
900 300 
800 800 
700 700 
600 600 
500 500 
400 ‘ 4 400 
300 EN é . . “ 300 
ae 6A 0 gTR 8A EAN 200 
100 o oe ae 100 
1800 1800 
ISOTHERMOHYPS. OCT. 8 1896. 

1700 1700 
1600 1600 
i500 doe 
1400 1400 
Ess 1300 
1200 1200 
1100 1100 
1000 1000 
‘900 Zits 
800 eae 
700 oS: 
600 600 
500 500 
400 ree 
ay 300 
200 on 
100 = 
Oo 


—L, 
HOURSS 2 ail 2 00S 4 5 aOR eS OD (Ol iene wel eS) (Glens en Sec Skee Ome ferme 


PLATE. V ET: 


ibe eosO re. VERIICAL Disa RIBUATON: 


METERS. = ' METERS 
1900 |__ es y a Ny ac 1900 
an | \ TEMPERATU RE. . __|1800 
1700 f_ ms ie a x a | 1700 
= | is } ‘ ye * ‘ 
1600 |_\ < | . - x N, % 1600 
1500 1500 
1400 : 6 1400 
1300 ‘ \ 1300 
1200 \ 1200 
1100 [ \ 1100 
1000 / 1000 
900 < / 900 
800 it 800 
a5 coe \ 700 
600 . \ | 600 
500 \ \ St 
a : 
400 ~ a0 
oS 
300 : ~ | 300 
. x 
00 . Ge | 200 
a ‘ x 
: Sa 
100 " Sen cot 100 
2 | ' ; | (Seren SL 0 
7 
DEGREES.=99 53 33 Sacks aes fore hie ino 
HUMIDITY, pce 
1900 
1800 
1700 
1600 
1500 
a 1400 
ames 
> > - 1300 
/ | 1200 
/ 1100 
/ | 
/ : 1000 
/ | 900 
/ | 800 
: | 
I 700 
. 600 
| \ 
l 500 
| * 
me : 
4 400 
| ine 
~ 300 
<< 
| ROME 
PER CT, 60 70. 40 50 25 35 40 50 60 70 80 
S 


PEATE WiTl: 


JU ay 


HARGRAVE 


EIDE J.0LaS 


4 


aosegtisas 


i 
eH 


tt 


Been w: 
Pet 


maa 


a 


Pir 


aga 


| 


af, 


“r 
by 
* 


is RICHARD # Impasse Fess ter PARIS Qe : 


RICHARD METEOROGRAPH. 


THERMOGRAPH USED IN 1894. 


1896-1897, 


EMPLOYED IN 


THE FIRST LIFTED BYA KITE. 


' 
A oe aps Ps 

’ ? : xs ‘5 

Li Smee oe 

: 7 J . a At , 


/ 
4 
re 
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